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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id g9-20020a170902c38900b001c7373769basm2074161plg.88.2023.09.28.20.24.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Sep 2023 20:24:36 -0700 (PDT) From: Kees Cook To: Eric Biederman Cc: Kees Cook , Sebastian Ott , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Pedro Falcato , Al Viro , Christian Brauner , Andrew Morton , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org Subject: [PATCH v4 1/6] binfmt_elf: Support segments with 0 filesz and misaligned starts Date: Thu, 28 Sep 2023 20:24:29 -0700 Message-Id: <20230929032435.2391507-1-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230929031716.it.155-kees@kernel.org> References: <20230929031716.it.155-kees@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" X-Developer-Signature: v=1; a=openpgp-sha256; l=8056; i=keescook@chromium.org; h=from:subject; bh=17HFsxzRR6qjNPl2OqeDyONMEClWu0Ld8l5K3CgB/PI=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlFkNx9ky4C5SoI1ZcjBN8kT+abWcWJ1uQcH9Lv 1XdD+58PfSJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZRZDcQAKCRCJcvTf3G3A Jkq+D/4+ERIwd+j9kCgE3YL8f6BaEPCM1Wy540egTRyd8uxuhJLV/MjU4bGQTq5IzynPij0EVRZ AMX3Kda0AuvJ9/nAqmFqVAPvO0yR68AwteJvc5m7SSBnbNIYr6LAJ4jO+2fBU/rx9GNhwZPe6dB blk7g6mbQXiRAeKTdqGu5bjoYcZTrrQFJj91tUj9OCuNDZEr2lD4iMNVPhZfK6HO97g2NWw11kt UEcNkn69PVA0KRsMgCqWh02zT9JvaZP+ciKiHEDz1aQoPHotcJpFQqEDxUSWkGUQwlkbKrGRaf1 fcPi2kq7GTJiTxXPgxd5o7yWriWxPHNTyhKGXcbmToLSeKJBOkj8NWQIkYlv05UyEUw+gY+0WZw FJ3LNMpBDzrKiUiNWUfal8Watcpz/yp+mjIELKSDFReTXTqLQW49KvqulWYNZHPtbpVVaTmkGGu bKCHrI4wlZo/0Ea4v4V205GrLpUsbdCcsj8CpSpWGlWqb+FWHvo0dQhWmwNQEWqpSA7soBBxKsV 5Ragq8YPGzA2Xl68fzMW7FnyZCLJOeob+5SPgEzYkdiUSqO3L0nZ2V8J5Xyxo3nxEyZ5KfjGyzU 8JgId+qHNCzcdvZSiOJ6nW3Io53wtMH4PaQZLa4PNAB19C3URkhNr/gqkDCFsv4txyd8mlojxjf NlBsHU/1WHut/KA== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Eric W. Biederman" Implement a helper elf_load() that wraps elf_map() and performs all of the necessary work to ensure that when "memsz > filesz" the bytes described by "memsz > filesz" are zeroed. An outstanding issue is if the first segment has filesz 0, and has a randomized location. But that is the same as today. In this change I replaced an open coded padzero() that did not clear all of the way to the end of the page, with padzero() that does. I also stopped checking the return of padzero() as there is at least one known case where testing for failure is the wrong thing to do. It looks like binfmt_elf_fdpic may have the proper set of tests for when error handling can be safely completed. I found a couple of commits in the old history https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git, that look very interesting in understanding this code. commit 39b56d902bf3 ("[PATCH] binfmt_elf: clearing bss may fail") commit c6e2227e4a3e ("[SPARC64]: Missing user access return value checks in= fs/binfmt_elf.c and fs/compat.c") commit 5bf3be033f50 ("v2.4.10.1 -> v2.4.10.2") Looking at commit 39b56d902bf3 ("[PATCH] binfmt_elf: clearing bss may fail"= ): > commit 39b56d902bf35241e7cba6cc30b828ed937175ad > Author: Pavel Machek > Date: Wed Feb 9 22:40:30 2005 -0800 > > [PATCH] binfmt_elf: clearing bss may fail > > So we discover that Borland's Kylix application builder emits weird e= lf > files which describe a non-writeable bss segment. > > So remove the clear_user() check at the place where we zero out the b= ss. I > don't _think_ there are any security implications here (plus we've ne= ver > checked that clear_user() return value, so whoops if it is a problem). > > Signed-off-by: Pavel Machek > Signed-off-by: Andrew Morton > Signed-off-by: Linus Torvalds It seems pretty clear that binfmt_elf_fdpic with skipping clear_user() for non-writable segments and otherwise calling clear_user(), aka padzero(), and checking it's return code is the right thing to do. I just skipped the error checking as that avoids breaking things. And notably, it looks like Borland's Kylix died in 2005 so it might be safe to just consider read-only segments with memsz > filesz an error. Reported-by: Sebastian Ott Reported-by: Thomas Wei=C3=9Fschuh Closes: https://lkml.kernel.org/r/20230914-bss-alloc-v1-1-78de67d2c6dd@weis= sschuh.net Signed-off-by: "Eric W. Biederman" Link: https://lore.kernel.org/r/87sf71f123.fsf@email.froward.int.ebiederm.o= rg Signed-off-by: Kees Cook Reviewed-by: Kees Cook Tested-by: Pedro Falcato --- fs/binfmt_elf.c | 111 +++++++++++++++++++++--------------------------- 1 file changed, 48 insertions(+), 63 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 7b3d2d491407..2a615f476e44 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -110,25 +110,6 @@ static struct linux_binfmt elf_format =3D { =20 #define BAD_ADDR(x) (unlikely((unsigned long)(x) >=3D TASK_SIZE)) =20 -static int set_brk(unsigned long start, unsigned long end, int prot) -{ - start =3D ELF_PAGEALIGN(start); - end =3D ELF_PAGEALIGN(end); - if (end > start) { - /* - * Map the last of the bss segment. - * If the header is requesting these pages to be - * executable, honour that (ppc32 needs this). - */ - int error =3D vm_brk_flags(start, end - start, - prot & PROT_EXEC ? VM_EXEC : 0); - if (error) - return error; - } - current->mm->start_brk =3D current->mm->brk =3D end; - return 0; -} - /* We need to explicitly zero any fractional pages after the data section (i.e. bss). This would contain the junk from the file that should not @@ -406,6 +387,51 @@ static unsigned long elf_map(struct file *filep, unsig= ned long addr, return(map_addr); } =20 +static unsigned long elf_load(struct file *filep, unsigned long addr, + const struct elf_phdr *eppnt, int prot, int type, + unsigned long total_size) +{ + unsigned long zero_start, zero_end; + unsigned long map_addr; + + if (eppnt->p_filesz) { + map_addr =3D elf_map(filep, addr, eppnt, prot, type, total_size); + if (BAD_ADDR(map_addr)) + return map_addr; + if (eppnt->p_memsz > eppnt->p_filesz) { + zero_start =3D map_addr + ELF_PAGEOFFSET(eppnt->p_vaddr) + + eppnt->p_filesz; + zero_end =3D map_addr + ELF_PAGEOFFSET(eppnt->p_vaddr) + + eppnt->p_memsz; + + /* Zero the end of the last mapped page */ + padzero(zero_start); + } + } else { + map_addr =3D zero_start =3D ELF_PAGESTART(addr); + zero_end =3D zero_start + ELF_PAGEOFFSET(eppnt->p_vaddr) + + eppnt->p_memsz; + } + if (eppnt->p_memsz > eppnt->p_filesz) { + /* + * Map the last of the segment. + * If the header is requesting these pages to be + * executable, honour that (ppc32 needs this). + */ + int error; + + zero_start =3D ELF_PAGEALIGN(zero_start); + zero_end =3D ELF_PAGEALIGN(zero_end); + + error =3D vm_brk_flags(zero_start, zero_end - zero_start, + prot & PROT_EXEC ? VM_EXEC : 0); + if (error) + map_addr =3D error; + } + return map_addr; +} + + static unsigned long total_mapping_size(const struct elf_phdr *phdr, int n= r) { elf_addr_t min_addr =3D -1; @@ -829,7 +855,6 @@ static int load_elf_binary(struct linux_binprm *bprm) struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata =3D NULL; struct elf_phdr *elf_property_phdata =3D NULL; unsigned long elf_bss, elf_brk; - int bss_prot =3D 0; int retval, i; unsigned long elf_entry; unsigned long e_entry; @@ -1040,33 +1065,6 @@ static int load_elf_binary(struct linux_binprm *bprm) if (elf_ppnt->p_type !=3D PT_LOAD) continue; =20 - if (unlikely (elf_brk > elf_bss)) { - unsigned long nbyte; - - /* There was a PT_LOAD segment with p_memsz > p_filesz - before this one. Map anonymous pages, if needed, - and clear the area. */ - retval =3D set_brk(elf_bss + load_bias, - elf_brk + load_bias, - bss_prot); - if (retval) - goto out_free_dentry; - nbyte =3D ELF_PAGEOFFSET(elf_bss); - if (nbyte) { - nbyte =3D ELF_MIN_ALIGN - nbyte; - if (nbyte > elf_brk - elf_bss) - nbyte =3D elf_brk - elf_bss; - if (clear_user((void __user *)elf_bss + - load_bias, nbyte)) { - /* - * This bss-zeroing can fail if the ELF - * file specifies odd protections. So - * we don't check the return value - */ - } - } - } - elf_prot =3D make_prot(elf_ppnt->p_flags, &arch_state, !!interpreter, false); =20 @@ -1162,7 +1160,7 @@ static int load_elf_binary(struct linux_binprm *bprm) } } =20 - error =3D elf_map(bprm->file, load_bias + vaddr, elf_ppnt, + error =3D elf_load(bprm->file, load_bias + vaddr, elf_ppnt, elf_prot, elf_flags, total_size); if (BAD_ADDR(error)) { retval =3D IS_ERR_VALUE(error) ? @@ -1217,10 +1215,8 @@ static int load_elf_binary(struct linux_binprm *bprm) if (end_data < k) end_data =3D k; k =3D elf_ppnt->p_vaddr + elf_ppnt->p_memsz; - if (k > elf_brk) { - bss_prot =3D elf_prot; + if (k > elf_brk) elf_brk =3D k; - } } =20 e_entry =3D elf_ex->e_entry + load_bias; @@ -1232,18 +1228,7 @@ static int load_elf_binary(struct linux_binprm *bprm) start_data +=3D load_bias; end_data +=3D load_bias; =20 - /* Calling set_brk effectively mmaps the pages that we need - * for the bss and break sections. We must do this before - * mapping in the interpreter, to make sure it doesn't wind - * up getting placed where the bss needs to go. - */ - retval =3D set_brk(elf_bss, elf_brk, bss_prot); - if (retval) - goto out_free_dentry; - if (likely(elf_bss !=3D elf_brk) && unlikely(padzero(elf_bss))) { - retval =3D -EFAULT; /* Nobody gets to see this, but.. */ - goto out_free_dentry; - } + current->mm->start_brk =3D current->mm->brk =3D ELF_PAGEALIGN(elf_brk); =20 if (interpreter) { elf_entry =3D load_elf_interp(interp_elf_ex, --=20 2.34.1 From nobody Sun Feb 8 04:14:08 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1A07BE743C0 for ; Fri, 29 Sep 2023 03:25:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232672AbjI2DZF (ORCPT ); Thu, 28 Sep 2023 23:25:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51056 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232545AbjI2DYn (ORCPT ); Thu, 28 Sep 2023 23:24:43 -0400 Received: from mail-pf1-x42f.google.com (mail-pf1-x42f.google.com [IPv6:2607:f8b0:4864:20::42f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA4D11A4 for ; Thu, 28 Sep 2023 20:24:41 -0700 (PDT) Received: by mail-pf1-x42f.google.com with SMTP id d2e1a72fcca58-692eed30152so7283916b3a.1 for ; Thu, 28 Sep 2023 20:24:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1695957881; x=1696562681; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=oGhwDBPbCWZ00dYqQrvOzcYwuI2lZJAyT/mcJzKB6R4=; b=LBbDvMAFsckb9rUyXHqwSaILl/O7qwOMEa1WpTcI0yWM+HphH0M3TBPUXTKkQPxFTX RWOprcE0u0X9RW2kTpY/AM16ftw2JaHliTAJpqkbKyRtaqCT1Obx34OjAGHxo244ed2a xY0/LKVe8n4KrLnr2iBdJFZdRGrSl2rhKJ7aY= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695957881; x=1696562681; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=oGhwDBPbCWZ00dYqQrvOzcYwuI2lZJAyT/mcJzKB6R4=; b=FTmHR6bTcl2RWPT9FzE25VwZ00rYKP8DU17iTyn5MKdDeczC//358JRyWP3+SNRyzC HqNjD0PuZmKlrOWd53ZZoLRYgPlMr62/9G8JA4128M9dhdGOYm+GzDMrDpgMurulb417 P5XHyVF4bMCPxCE9vhN84VuwunUbaXXAx479LN4ywS988Zc21mIPs4AUwPuAEsZYscxF IMaUyZhdOLg5YLAG9pSiG1wERTh6wB4IOrgxNBJ5MjKA5QGYO1Em/bEOm/21GLssOXBA KL5+ff1kYPE6slcfXodxLWQTu3B1hs8fW6vEhYierYUX2tsMuDgc95EfRoItLBH1MjX7 m/MQ== X-Gm-Message-State: AOJu0YwQiuLwUgzBvtK0ijeAfDwmh/yPxaBAsB/qW7ZYp7WEiLAe82ZL oC2+1qbZzdE9+Y2NnnQHIbrK5g== X-Google-Smtp-Source: AGHT+IEefjdEHzDxwiSxbmO/u6TF6zB5AljlbT04olaKMdKQR8C/b8AJwKo7ESYTNvbBR3eWZ847tQ== X-Received: by 2002:a05:6a00:190e:b0:690:ce30:47ba with SMTP id y14-20020a056a00190e00b00690ce3047bamr2938508pfi.10.1695957881184; Thu, 28 Sep 2023 20:24:41 -0700 (PDT) Received: from www.outflux.net (198-0-35-241-static.hfc.comcastbusiness.net. [198.0.35.241]) by smtp.gmail.com with ESMTPSA id s26-20020aa78d5a000000b00672ea40b8a9sm14427552pfe.170.2023.09.28.20.24.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Sep 2023 20:24:39 -0700 (PDT) From: Kees Cook To: Eric Biederman Cc: Kees Cook , Alexander Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Sebastian Ott , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Pedro Falcato , Andrew Morton , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v4 2/6] binfmt_elf: elf_bss no longer used by load_elf_binary() Date: Thu, 28 Sep 2023 20:24:30 -0700 Message-Id: <20230929032435.2391507-2-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230929031716.it.155-kees@kernel.org> References: <20230929031716.it.155-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1738; i=keescook@chromium.org; h=from:subject; bh=G8gKivjP+bPsGdacm75CduzZVarN6sAt0dfrtCVUjtY=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlFkNx2BuLhX7iIAkgIu+LW3P3r4pxnZlwRaDRf vA/0AICBj2JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZRZDcQAKCRCJcvTf3G3A JpKyD/9/zd7E+5U1dJPLc6FAk+4qelFfCB75a77Kwxx0x/dnFrrOEedqqpaOK3ve3TybifJrVjE h8wTDDoxua66DT705EB1I4t9hKVj7ivb1dRVQdU3WehX4HAJzhPWJ7EtDjtX4AeM5D+Hf7hDpz4 hfwpwEYxXXAs73zeYWM19Na85lFwu6nSgf/ttA5F2ewH+beQAvHkMQN6gO9tp95OrFyS1MZdXBI NrkU9qg/ruk3uLO2OsVV6oDaLOu79M+4Kf6narATryoLsN4PLTkC8vQrd2qtvfiFgrJMPpbfCn8 mEteP/5U+mKLFaCYdxhauFlCzaPVAwvY9GsSaOxsm+ilLLoz76BgaZJ3mTlmC1hryS1DfX5TNYm BmEtiulolRPfz4jsO8ynBLlG9W3OMzNzN8tAFwtRv5C9pp0Y+Fp2Q4+kBwt72QGCQLH4GAe0o9t m4EhUZsGXS3t3VJlwU/3NoxBNO9bz5DuQRp5K6qTCwsnbFMQXMIL3xR1Vd0jwfPPrscAtd+3IlT pbesK8GLRSzYSy4YOE92dGY+Av5QlXCA+DMcppAI/si2TTqnM19+SkKDASB7HwxP2YQiCADAV3U 67MufnT9YBLfq2RWMu1o2nR3+x4f5uWbDtEvSPRE7Ki8QD8I5Ldh64XqqxhTjKdmqEPIl7TvgC2 QoH6u6C/JkEFAwQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" With the BSS handled generically via the new filesz/memsz mismatch handling logic in elf_load(), elf_bss no longer needs to be tracked. Drop the variable. Cc: Eric Biederman Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Suggested-by: Eric Biederman Signed-off-by: Kees Cook Reviewed-by: Kees Cook Tested-by: Pedro Falcato --- fs/binfmt_elf.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 2a615f476e44..0214d5a949fc 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -854,7 +854,7 @@ static int load_elf_binary(struct linux_binprm *bprm) unsigned long error; struct elf_phdr *elf_ppnt, *elf_phdata, *interp_elf_phdata =3D NULL; struct elf_phdr *elf_property_phdata =3D NULL; - unsigned long elf_bss, elf_brk; + unsigned long elf_brk; int retval, i; unsigned long elf_entry; unsigned long e_entry; @@ -1045,7 +1045,6 @@ static int load_elf_binary(struct linux_binprm *bprm) if (retval < 0) goto out_free_dentry; =20 - elf_bss =3D 0; elf_brk =3D 0; =20 start_code =3D ~0UL; @@ -1208,8 +1207,6 @@ static int load_elf_binary(struct linux_binprm *bprm) =20 k =3D elf_ppnt->p_vaddr + elf_ppnt->p_filesz; =20 - if (k > elf_bss) - elf_bss =3D k; if ((elf_ppnt->p_flags & PF_X) && end_code < k) end_code =3D k; if (end_data < k) @@ -1221,7 +1218,6 @@ static int load_elf_binary(struct linux_binprm *bprm) =20 e_entry =3D elf_ex->e_entry + load_bias; phdr_addr +=3D load_bias; - elf_bss +=3D load_bias; elf_brk +=3D load_bias; start_code +=3D load_bias; end_code +=3D load_bias; --=20 2.34.1 From nobody Sun Feb 8 04:14:08 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 763B5E743C0 for ; Fri, 29 Sep 2023 03:25:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232666AbjI2DY6 (ORCPT ); Thu, 28 Sep 2023 23:24:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51070 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232426AbjI2DYo (ORCPT ); Thu, 28 Sep 2023 23:24:44 -0400 Received: from mail-qk1-x72a.google.com (mail-qk1-x72a.google.com [IPv6:2607:f8b0:4864:20::72a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CD49C199 for ; Thu, 28 Sep 2023 20:24:40 -0700 (PDT) Received: by mail-qk1-x72a.google.com with SMTP id af79cd13be357-7742da399a2so624678185a.0 for ; Thu, 28 Sep 2023 20:24:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1695957880; x=1696562680; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=7JCtI6Mw9jLbpCfzTWeYqaol0MCiq7teZQqSoN5bxO4=; b=PAEZ/ez4XM+Nfd7IxqcYrATv76QfWiEkrKWgea+lJzL31QWfywvX55Hr196SMSWJv2 H+tdJI+HyacXvcIeNp6Xwg12Gxfp9T1WzOP7CBBIDiCRmh3z9klBb8Zqmb62ID6ugxzS /Bxt6UgTKJOkP4uKTqSctiHKw+9ZTNqwBg3ts= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695957880; x=1696562680; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=7JCtI6Mw9jLbpCfzTWeYqaol0MCiq7teZQqSoN5bxO4=; b=EOS6qjUi2GYQ6ylOCxzkPgg1ZjHDgpnR9sd6cLj80UhymSWXvYCF9N0AJsyYRhP8pr GVf0p//sUMOQn6aLtdHrzUmKFBAWpYx6dV66q7QeMUNEAdYt881RWt6wV9mz7x20nerw JL16VYpa4rdeTGLFekw9JiEWInXztSK2aZED0fAhbkFIqy4LpkXQli7xNAOx3u6yX3OO +35JkHl+jQVpWAnyXB1QBct1LJ9utL1m27DxbuB8I8vOtiuxr986ziMaODu0GF2bCId7 ouA6Uqze1upk9z6+fHtO1IRUVWlNlrncw4jbC5GQUdMQpVWw/M4phbmWZ7oi81S9wJR8 ks2Q== X-Gm-Message-State: AOJu0YzMiuY952OPr7pDw7JRd54k7AMHO7oc47yma7YFOWTOWV7izQ0v KFkgjPrJWbFUDXaHkHtGUifORw== X-Google-Smtp-Source: AGHT+IELcqZMMKb1td/vncjB5sH12I54PHU5TdsvQyhNwOMv+fB/QBhAjEGhxQYK020wITjebfX9sQ== X-Received: by 2002:a05:620a:e9d:b0:772:6443:daf3 with SMTP id w29-20020a05620a0e9d00b007726443daf3mr2738735qkm.66.1695957879917; Thu, 28 Sep 2023 20:24:39 -0700 (PDT) Received: from www.outflux.net (198-0-35-241-static.hfc.comcastbusiness.net. [198.0.35.241]) by smtp.gmail.com with ESMTPSA id du14-20020a056a002b4e00b00690fe1c928esm10256201pfb.91.2023.09.28.20.24.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Sep 2023 20:24:36 -0700 (PDT) From: Kees Cook To: Eric Biederman Cc: Kees Cook , Alexander Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Pedro Falcato , Sebastian Ott , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Andrew Morton , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v4 3/6] binfmt_elf: Use elf_load() for interpreter Date: Thu, 28 Sep 2023 20:24:31 -0700 Message-Id: <20230929032435.2391507-3-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230929031716.it.155-kees@kernel.org> References: <20230929031716.it.155-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2936; i=keescook@chromium.org; h=from:subject; bh=8mN64ZnApkL7mlS3J3j8M/PeeHjiU24xpvEFIwO52Sc=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlFkNyQ5p5E4Tg789OjEFFGvDw6hy8O/CboaqJO +gn/YtsP02JAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZRZDcgAKCRCJcvTf3G3A JlfrD/0UmFIiwvqM26CPsRIStoMfmoWWLE+1T0+B6VIpoHHYl6fxgrYIk1GMjuaGbD0RwF9QP+t BqcWROGSbE7jtsk5rW33lmv5P4kATjv1E8P0xTh6YLwy/qmxm1iBcqH7A7aIp5rT/ZZxmRWS7z/ KaumFG9s9XzIzz7vNtyCpYAslNBn7Ct0D760d/KdyUyF0tRcwUZGbbqsCSJ3qDlqi9Oh48d8rqr zVrOdBbcoN0GFz2NFhwg1g0iypiVC72gYNSKuCVuYoSflzMWmk+MWWz+KoGHh8QQyufk09tUrRt 7e7QzVJPtxRfKGiVSBnbT7mPxw87BCa7B1z+sX5Sj7D4++z7rbKsnwJGiOeSn9hRsn3zwU/bHKg 2VugFFQ+5/llgN3z58QGPu56dO6ydWYCZeneBcrQoNc1xhZyz8M2IpA5m0iJS719hxg22R2fW1p xaQITu1kMm0y6BxdReD/XHhw3eM0HzXWV9ltG8nLrJXOVz5Ve3z1wcEusMGPOh07NsX6dEfXDJv XYtMF21/+UxnZ3eYxaWMHimE+Qo2DtB694DxSqJhwRK4FB4KUShHOAsbSQTcGSzXCx13gP3vhF0 S8eSoWkYBz90zkFWSPCcyq4F9jfXjVmVgHQgU/leUKWz2vDzeEVdmX04CQNaCQPS6MFWyGJaKml bTMeDeMtwCCfvfQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Handle arbitrary memsz>filesz in interpreter ELF segments, instead of only supporting it in the last segment (which is expected to be the BSS). Cc: Eric Biederman Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Reported-by: Pedro Falcato Closes: https://lore.kernel.org/lkml/20221106021657.1145519-1-pedro.falcato= @gmail.com/ Signed-off-by: Kees Cook Reviewed-by: Kees Cook Tested-by: Pedro Falcato --- fs/binfmt_elf.c | 46 +--------------------------------------------- 1 file changed, 1 insertion(+), 45 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 0214d5a949fc..db47cb802f89 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -622,8 +622,6 @@ static unsigned long load_elf_interp(struct elfhdr *int= erp_elf_ex, struct elf_phdr *eppnt; unsigned long load_addr =3D 0; int load_addr_set =3D 0; - unsigned long last_bss =3D 0, elf_bss =3D 0; - int bss_prot =3D 0; unsigned long error =3D ~0UL; unsigned long total_size; int i; @@ -660,7 +658,7 @@ static unsigned long load_elf_interp(struct elfhdr *int= erp_elf_ex, else if (no_base && interp_elf_ex->e_type =3D=3D ET_DYN) load_addr =3D -vaddr; =20 - map_addr =3D elf_map(interpreter, load_addr + vaddr, + map_addr =3D elf_load(interpreter, load_addr + vaddr, eppnt, elf_prot, elf_type, total_size); total_size =3D 0; error =3D map_addr; @@ -686,51 +684,9 @@ static unsigned long load_elf_interp(struct elfhdr *in= terp_elf_ex, error =3D -ENOMEM; goto out; } - - /* - * Find the end of the file mapping for this phdr, and - * keep track of the largest address we see for this. - */ - k =3D load_addr + eppnt->p_vaddr + eppnt->p_filesz; - if (k > elf_bss) - elf_bss =3D k; - - /* - * Do the same thing for the memory mapping - between - * elf_bss and last_bss is the bss section. - */ - k =3D load_addr + eppnt->p_vaddr + eppnt->p_memsz; - if (k > last_bss) { - last_bss =3D k; - bss_prot =3D elf_prot; - } } } =20 - /* - * Now fill out the bss section: first pad the last page from - * the file up to the page boundary, and zero it from elf_bss - * up to the end of the page. - */ - if (padzero(elf_bss)) { - error =3D -EFAULT; - goto out; - } - /* - * Next, align both the file and mem bss up to the page size, - * since this is where elf_bss was just zeroed up to, and where - * last_bss will end after the vm_brk_flags() below. - */ - elf_bss =3D ELF_PAGEALIGN(elf_bss); - last_bss =3D ELF_PAGEALIGN(last_bss); - /* Finally, if there is still more bss to allocate, do it. */ - if (last_bss > elf_bss) { - error =3D vm_brk_flags(elf_bss, last_bss - elf_bss, - bss_prot & PROT_EXEC ? VM_EXEC : 0); - if (error) - goto out; - } - error =3D load_addr; out: return error; --=20 2.34.1 From nobody Sun Feb 8 04:14:08 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84B8CE743DC for ; Fri, 29 Sep 2023 03:24:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232560AbjI2DYo (ORCPT ); Thu, 28 Sep 2023 23:24:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51012 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232321AbjI2DYl (ORCPT ); Thu, 28 Sep 2023 23:24:41 -0400 Received: from mail-pf1-x434.google.com (mail-pf1-x434.google.com [IPv6:2607:f8b0:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8D55D1AA for ; Thu, 28 Sep 2023 20:24:39 -0700 (PDT) Received: by mail-pf1-x434.google.com with SMTP id d2e1a72fcca58-692d2e8c003so152778b3a.1 for ; Thu, 28 Sep 2023 20:24:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1695957879; x=1696562679; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=95+jGh9HzPfjIjeeQbyhCMVgDdqV+t+zi0ml5yOYuB8=; b=jxYfHi6UrmlN+2RUW3BFPUPF6/N0gHYlZIWZzjNHw7WzqWZzyCSQIRcCf7rXysywY3 s1yOxdFMqC5M6da9Zpq4ZD/D53DypziHPfjATX/sfflu3nUOB5j8/C0VJBMaHXLMRUrV CLytRsuOuOhoJWKJqFJCuVH8yPGfPTe1n9hmw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695957879; x=1696562679; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=95+jGh9HzPfjIjeeQbyhCMVgDdqV+t+zi0ml5yOYuB8=; b=fXNxYNXXC7ydaKD5S0tX+0IPGcSwKxp/i2UjcXgixYNgx8pidXvkZvaF4PJ4fkrOOm I4HbLrRY3zEDK6Vo1oCoouPT/VbnrAsqEpx4v8+blyMvAjO0sQBBJJ6eMLCyzYiN9zD5 V10DZbIkGuDSGDA8JfITge1wYXWGTTtPDJ/GMdQFbkuf0FI05ElmvCNxfHp5+oG3SnAz BVGC/Kljm1wPMJuz/RiuIObytDTSAfRvhGppHN7/7TgeCnpfuQ5QXPU4gNQ3zKcrZSmR Msu7rOlwqhQmV4oBXSgq7eiXKpwa5+gdeAwett3b3OwQlhFWkHt7XFa+xb0BUiCcqSYr iV5A== X-Gm-Message-State: AOJu0YxL/keAGbnEjoMaMCPpcGOQrEURuMlnDt35wMsf+AWIp+yL47h7 /wbfqxPftfcsDnY/0WWlqBkJoA== X-Google-Smtp-Source: AGHT+IENptQn7XIn+gHi7Xk/Rom3FrwjZlYNl2dbdfUf0uD5PWaNHfgd4GwUs3Rvuj8dtt6Ixw6ezw== X-Received: by 2002:a05:6a20:72a5:b0:153:4ea6:d12e with SMTP id o37-20020a056a2072a500b001534ea6d12emr5304382pzk.17.1695957878823; Thu, 28 Sep 2023 20:24:38 -0700 (PDT) Received: from www.outflux.net (198-0-35-241-static.hfc.comcastbusiness.net. [198.0.35.241]) by smtp.gmail.com with ESMTPSA id b5-20020aa78705000000b0068ff267f094sm3481738pfo.158.2023.09.28.20.24.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Sep 2023 20:24:36 -0700 (PDT) From: Kees Cook To: Eric Biederman Cc: Kees Cook , Alexander Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Sebastian Ott , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Pedro Falcato , Andrew Morton , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v4 4/6] binfmt_elf: Use elf_load() for library Date: Thu, 28 Sep 2023 20:24:32 -0700 Message-Id: <20230929032435.2391507-4-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230929031716.it.155-kees@kernel.org> References: <20230929031716.it.155-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1627; i=keescook@chromium.org; h=from:subject; bh=HDRWJgiZi2B41NjfcoHun/GXVPB8PhMH+K8nRgD/QEY=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlFkNyd7onj53UAnvTrNuqjrOoqdzlhhnL6T0n4 waDipxrCuyJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZRZDcgAKCRCJcvTf3G3A JgqhEACQaxzh9TUbPcDbZo8niTtocmDdmljr+QUAo/kUcZsO7WwVGlruTUeAl3DsFH2PvI/7f8q 6Gzf2F516CRNsoFBvkxeJHFWa21p4CjiRwEYH+rdFGIQwe4ZXPrdSrcJhWVB35JNjqR8CK/aRK2 NAJeh7WuuaTnpcDhFmPiXWQuRt1noAczm74SRZU8IZ06ucQ49FNFgl7FPCGA0RLuWRQDEc4zXaQ BQktUi2h0of64YlxMdZfk+SQMGz2lOqO7a3F8Zy9PazbSnHb5k2NrkreHnNxtncdID9uE6SiKy+ JVJ8/BMveYU1W8I+asdhp8xe2CV19g1Qmlq4ZVCoeGxeV9OtFE+c8gjwaTlFdRjzRgfVqvqVmtp OYM3ExS5b6+tEeavoEpUw88foXpj9yoZLMwL8pVfsXc2FYIlPsrtaFfUyacQhttqevffosf/oUf bksChMr+i07cgy1L/yGOx/6wCfvU8HTwH+VMXDpSSowba7S7GbBmvxw9EtoVWjqJAGNdtQ6FvJZ 6SXLe7ag42PtcuMWe8C14GuF1yYIcvu/o/vpy24R3zfZUovoJAGPuns5yKBok4/GV2c31zPoB/p 5ZXXOtl28un+F7p/qF9lnnk6I8GbyO4YgCPqLeXph77PUUZfI4r38oOBt9/p+hKk0yQ+7nD6eH+ 8MpI/toIRLPKXkg== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" While load_elf_library() is a libc5-ism, we can still replace most of its contents with elf_load() as well, further simplifying the code. Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Suggested-by: Eric Biederman Signed-off-by: Kees Cook Reviewed-by: Kees Cook Tested-by: Pedro Falcato --- fs/binfmt_elf.c | 23 ++++------------------- 1 file changed, 4 insertions(+), 19 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index db47cb802f89..f8b4747f87ed 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -1351,30 +1351,15 @@ static int load_elf_library(struct file *file) eppnt++; =20 /* Now use mmap to map the library into memory. */ - error =3D vm_mmap(file, - ELF_PAGESTART(eppnt->p_vaddr), - (eppnt->p_filesz + - ELF_PAGEOFFSET(eppnt->p_vaddr)), + error =3D elf_load(file, ELF_PAGESTART(eppnt->p_vaddr), + eppnt, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_FIXED_NOREPLACE | MAP_PRIVATE, - (eppnt->p_offset - - ELF_PAGEOFFSET(eppnt->p_vaddr))); - if (error !=3D ELF_PAGESTART(eppnt->p_vaddr)) - goto out_free_ph; + 0); =20 - elf_bss =3D eppnt->p_vaddr + eppnt->p_filesz; - if (padzero(elf_bss)) { - error =3D -EFAULT; + if (error !=3D ELF_PAGESTART(eppnt->p_vaddr)) goto out_free_ph; - } =20 - len =3D ELF_PAGEALIGN(eppnt->p_filesz + eppnt->p_vaddr); - bss =3D ELF_PAGEALIGN(eppnt->p_memsz + eppnt->p_vaddr); - if (bss > len) { - error =3D vm_brk(len, bss - len); - if (error) - goto out_free_ph; - } error =3D 0; =20 out_free_ph: --=20 2.34.1 From nobody Sun Feb 8 04:14:08 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50F73E743C0 for ; Fri, 29 Sep 2023 03:25:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232470AbjI2DZP (ORCPT ); Thu, 28 Sep 2023 23:25:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51414 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232600AbjI2DYv (ORCPT ); Thu, 28 Sep 2023 23:24:51 -0400 Received: from mail-pg1-x530.google.com (mail-pg1-x530.google.com [IPv6:2607:f8b0:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0EC3B1B1 for ; Thu, 28 Sep 2023 20:24:43 -0700 (PDT) Received: by mail-pg1-x530.google.com with SMTP id 41be03b00d2f7-517ab9a4a13so9931669a12.1 for ; Thu, 28 Sep 2023 20:24:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1695957882; x=1696562682; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=1N2/5RenlXFMtuBqo/+f8Vcn16/Uj2Iw7MwFuqiNorY=; b=gHYyAdOoo9+Uq0fM+3FDoaZjk+aghJ6WPsGkXPszGftW8VjFFXzy5d93L9aLeFwAyd ni2RloEREBWicKL8qFOb2QZyUIzcTVsLW+9zzyU9fq5euZ9xVNh3PaRWTcV5nw//82Pq yL9rgN+tzJFgm0KSeoLGYfnpud/KR5kuELKag= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695957882; x=1696562682; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=1N2/5RenlXFMtuBqo/+f8Vcn16/Uj2Iw7MwFuqiNorY=; b=nQygZyECE3sL9zFDdJ3Ot4Ylx6NshH/pWfsbXzrVmx8X601p8oCVDZrMWFDoWhh3bl IubMA5t9hXdH6hTmb6Xk6waYdxemYdXAs2xnZODXN2kKcgVGg3Qyd337cwrWzRnXSVid puxheqdd3qADMQvZhQsEyCiUb+7gB4JCK4+NpijoiWNxmiaqKpRw2o0ooPkEVaDiuOR6 kMgnoicIP3dO+Oun0eYCPC8TGAHaaVIJMiXoXQmFkBj5GktDvHxggMhqUhd9oUMYGO8T tftLaFpzhcZFNo+OSlaJ5aAzyjhoF3j9UC6a7x483DMwftcNBTmOaw30ZXRm3pCzsPp+ yBAw== X-Gm-Message-State: AOJu0Yzl6mM/7LvCPHgQzZbvBCWdtk9Gg4YA7DOpWTNESPL1DHMMAAm6 9H56atSaXZ7Ia+/5Uu0TW9xzoQ== X-Google-Smtp-Source: AGHT+IFuiY5V1hPcrjWZ+wALbwRJ0bkGU805RDV1GGRAKG36PeI1WQG0N/Q94yXBG5u0guRkQHN2ew== X-Received: by 2002:a05:6a21:6d90:b0:162:d056:9f52 with SMTP id wl16-20020a056a216d9000b00162d0569f52mr2317143pzb.14.1695957882509; Thu, 28 Sep 2023 20:24:42 -0700 (PDT) Received: from www.outflux.net (198-0-35-241-static.hfc.comcastbusiness.net. [198.0.35.241]) by smtp.gmail.com with ESMTPSA id d12-20020a17090a498c00b0026b3ed37ddcsm297774pjh.32.2023.09.28.20.24.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Sep 2023 20:24:39 -0700 (PDT) From: Kees Cook To: Eric Biederman Cc: Kees Cook , Alexander Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Sebastian Ott , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Pedro Falcato , Andrew Morton , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v4 5/6] binfmt_elf: Only report padzero() errors when PROT_WRITE Date: Thu, 28 Sep 2023 20:24:33 -0700 Message-Id: <20230929032435.2391507-5-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230929031716.it.155-kees@kernel.org> References: <20230929031716.it.155-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3206; i=keescook@chromium.org; h=from:subject; bh=jt1fmczJcOormxbVcL/G+gA6YgAS2bIpzH9lxZKP6J8=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlFkNyRwIKy/9+p28ZJ729vcNHK8Gg7yPfE0ByN 6nvj7/qVLeJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZRZDcgAKCRCJcvTf3G3A JjvTD/0efjaJu1+PNkM8NRGdk1dsGyZJ0dd4tY+8HW5FWR8J7niOASg788NVSLqFFUmdhaHRjmO Lj56b26Bw9GOyQXHYda5l7wqDTMXm6RIMUYBjTHTuUu3K8IYicpe/vidGvDuun74TWC6gT0TcQS JBtpkVYUzN9Quzlr+hjKY4YwSAMa+50O1SYTdUGqwmckLYkIpbbwVLAo7r/VX4KL73ojipa0uZL U4Z96HcimN4eOgUTJL+Z0t4VxznrtCujhN04154vNUcC1vzmWqEyPkrIaegDJh86UloTxqH/Esa mEVSbpK9HjAWKRRsvhfOPp2btfPm3150XfvwHXXipw4qVDOWOWYhb7tHCVoYriEG/H0nn5qroT1 PIRndidx60sCNBiIR++8QGxeZhVypD2rtBlFMJYxk8hREnuCOUIUakD1s4SmYoqYAa/N6j10yfn USW7wazw7KE0x/SHGyklD7+FJFIHi/dFaGRXo6PdpXd2O8m/Fnh82Px9LxMZldJtVxrwmm2YcUb AIegTgqbd3pR1GCUvhncdf3yEUBwywr6llI4pfc2Bpc4oznxAVKNeJoY5hIrwCbXVKuO54wkBIg dP9Sl+hc6k26DlLVynWraFAeBWkU+QBlgtEZI18h+WBXWKlb9zkdhbKOcrAovas3JG4CcT3Onsb u68NsqyzQBTv3nw== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Errors with padzero() should be caught unless we're expecting a pathological (non-writable) segment. Report -EFAULT only when PROT_WRITE is present. Additionally add some more documentation to padzero(), elf_map(), and elf_load(). Cc: Eric Biederman Cc: Alexander Viro Cc: Christian Brauner Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Suggested-by: Eric Biederman Signed-off-by: Kees Cook Reviewed-by: Kees Cook Tested-by: Pedro Falcato --- fs/binfmt_elf.c | 32 +++++++++++++++++++++++--------- 1 file changed, 23 insertions(+), 9 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index f8b4747f87ed..22027b0a5923 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -110,19 +110,19 @@ static struct linux_binfmt elf_format =3D { =20 #define BAD_ADDR(x) (unlikely((unsigned long)(x) >=3D TASK_SIZE)) =20 -/* We need to explicitly zero any fractional pages - after the data section (i.e. bss). This would - contain the junk from the file that should not - be in memory +/* + * We need to explicitly zero any trailing portion of the page that follows + * p_filesz when it ends before the page ends (e.g. bss), otherwise this + * memory will contain the junk from the file that should not be present. */ -static int padzero(unsigned long elf_bss) +static int padzero(unsigned long address) { unsigned long nbyte; =20 - nbyte =3D ELF_PAGEOFFSET(elf_bss); + nbyte =3D ELF_PAGEOFFSET(address); if (nbyte) { nbyte =3D ELF_MIN_ALIGN - nbyte; - if (clear_user((void __user *) elf_bss, nbyte)) + if (clear_user((void __user *)address, nbyte)) return -EFAULT; } return 0; @@ -348,6 +348,11 @@ create_elf_tables(struct linux_binprm *bprm, const str= uct elfhdr *exec, return 0; } =20 +/* + * Map "eppnt->p_filesz" bytes from "filep" offset "eppnt->p_offset" + * into memory at "addr". (Note that p_filesz is rounded up to the + * next page, so any extra bytes from the file must be wiped.) + */ static unsigned long elf_map(struct file *filep, unsigned long addr, const struct elf_phdr *eppnt, int prot, int type, unsigned long total_size) @@ -387,6 +392,11 @@ static unsigned long elf_map(struct file *filep, unsig= ned long addr, return(map_addr); } =20 +/* + * Map "eppnt->p_filesz" bytes from "filep" offset "eppnt->p_offset" + * into memory at "addr". Memory from "p_filesz" through "p_memsz" + * rounded up to the next page is zeroed. + */ static unsigned long elf_load(struct file *filep, unsigned long addr, const struct elf_phdr *eppnt, int prot, int type, unsigned long total_size) @@ -404,8 +414,12 @@ static unsigned long elf_load(struct file *filep, unsi= gned long addr, zero_end =3D map_addr + ELF_PAGEOFFSET(eppnt->p_vaddr) + eppnt->p_memsz; =20 - /* Zero the end of the last mapped page */ - padzero(zero_start); + /* + * Zero the end of the last mapped page but ignore + * any errors if the segment isn't writable. + */ + if (padzero(zero_start) && (prot & PROT_WRITE)) + return -EFAULT; } } else { map_addr =3D zero_start =3D ELF_PAGESTART(addr); --=20 2.34.1 From nobody Sun Feb 8 04:14:08 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B562E743C0 for ; Fri, 29 Sep 2023 03:25:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232678AbjI2DZK (ORCPT ); Thu, 28 Sep 2023 23:25:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51396 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232596AbjI2DYu (ORCPT ); Thu, 28 Sep 2023 23:24:50 -0400 Received: from mail-pj1-x102d.google.com (mail-pj1-x102d.google.com [IPv6:2607:f8b0:4864:20::102d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 368D219C for ; Thu, 28 Sep 2023 20:24:42 -0700 (PDT) Received: by mail-pj1-x102d.google.com with SMTP id 98e67ed59e1d1-27752a1e184so7985881a91.3 for ; Thu, 28 Sep 2023 20:24:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; t=1695957881; x=1696562681; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=+wPEhWpvRY896Xnw5Ev1/y00zI5fAQGyVN5RsYugNn8=; b=QIPJhQmPgqMaezjOXQu9ufOmTKlnJYeYRBnC/L59my/pZbXCnc0RWylCjiZ3ymcOkJ LWZpFCY0T/PBct+kWcmVACzEjG/mtT3nN/shP/UZlrbjlVLQlJMukDG5/54WFFl1FZDM XxJBi9w42no+IBnHSdFzxtp2hu5/Yd+gnBi8s= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695957881; x=1696562681; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=+wPEhWpvRY896Xnw5Ev1/y00zI5fAQGyVN5RsYugNn8=; b=cnjHQ+jo8FuEu0q9VB0UDznW3f4e0TnnqOdLtH88iVUW0DoXDpemaOlZpOVJqL/bdo hiTTIX7imFXzanLsoX6s/v+MLkVja5geyLZgryqFwW803vUTzRMNEBs/uiZ36j6XL+ur KXuJTxV4iGx24X3JRkBTH6wsWAgsnMH9hXRrqSOwFvL7KLAWWDHcja5MWkTRtuxjWeOV VtIi6pI40FO95NRrckrPyIca6sUNACW+k4OLb0UUbWYdlqRFRjPUtmbQSnXCXdxAP1Ou dfrv3SwhTsR8MRaAP5ffoz426rdNmnoqEgl0WAK8DpYA8gcx+TAulXQAwfU0jXLTvYAB mx0g== X-Gm-Message-State: AOJu0YyVJPze0uV6Wjw3Tj4ICb8YPGFuk6pmjwZ2AHIMqueL93lDV1Om gOWlj8mBWyriRLuIka8sW2TrDw== X-Google-Smtp-Source: AGHT+IGrJvdYK0UubFjOkgcsulZp4Iwd9Tt7tIAbT+bREXfQrb6kahqghubh3CtXHQN6f3Ye2DXCOA== X-Received: by 2002:a17:90a:ba92:b0:267:ffcf:e9e3 with SMTP id t18-20020a17090aba9200b00267ffcfe9e3mr3087478pjr.46.1695957881706; Thu, 28 Sep 2023 20:24:41 -0700 (PDT) Received: from www.outflux.net (198-0-35-241-static.hfc.comcastbusiness.net. [198.0.35.241]) by smtp.gmail.com with ESMTPSA id x15-20020a17090a530f00b0027654d389casm297683pjh.54.2023.09.28.20.24.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 28 Sep 2023 20:24:39 -0700 (PDT) From: Kees Cook To: Eric Biederman Cc: Kees Cook , Andrew Morton , linux-mm@kvack.org, Sebastian Ott , =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= , Pedro Falcato , Al Viro , Christian Brauner , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v4 6/6] mm: Remove unused vm_brk() Date: Thu, 28 Sep 2023 20:24:34 -0700 Message-Id: <20230929032435.2391507-6-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230929031716.it.155-kees@kernel.org> References: <20230929031716.it.155-kees@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2050; i=keescook@chromium.org; h=from:subject; bh=qQgWJ2LfzVKqVSy79Ld0II87Ub3I62svbZlMXS8eqNU=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlFkNyozNMKFDP2i80754Px/+ZY/Cx7wBo4sXmZ GfAFEgqokWJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZRZDcgAKCRCJcvTf3G3A JvugEAC1X9CtGDjUrVOsqG0t9TTnzkbAODtZErc43R+VjV7tM+wgC1YoBq1uGKg3kk/39J5ROiJ rUkABHj3UilMN33EplFoDi9bG/ErY91MQttOzzjtGtjVqWIrEJ/Vl9Txp0Lfb8zYFy9NsK/6FUL MtgFp5sk40k0qU96E6p96fB7SzEc44a33CLYYExFKVE2M08Bylw2aJ9Ee0dsno2XN3kwHuLByFf wcJ9XIEkkKA6ek8B7IuLsRGmbigeQnoNgTo87K5bPOqAGNyvV5AaKea9aX90W7XTFl3Mg767UDU QBSQvaLWv+t6WEIH+DBweDTKSOHJsyAOniUBtf5ZYA37xZuqPVJdtHMHNT5eperaA7H3rjw+UUz Jlq6iSEPSQzB/ur6ucWrK0s4O62amvSspv633OZXBOo6liFA9krixvk0n9DDIpK4izJk9sqIro1 JU8Wshi103umj8FDzYRXujBj+g//VNypVJAxw30ltepS01lpNn33UpY/bazcxEBWtzAI6WzksOn OioMLo/fYEk9tr3WtHRgTsp7V0afPDYJ6aOpeBzZjAdyfqtuIfngMDD8ITow2mnQdSypEQ39K9p Rr6tuk/SEYKG3c/cQmyk7L+/cRTRAgeeYxAnZFNKbHqj7DeGYfmOdb6oTSlHNHgU9S+L8PRk5BL FEozwXjpMVEPE4w== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" With fs/binfmt_elf.c fully refactored to use the new elf_load() helper, there are no more users of vm_brk(), so remove it. Cc: Andrew Morton Cc: linux-mm@kvack.org Suggested-by: Eric Biederman Signed-off-by: Kees Cook Reviewed-by: Kees Cook Tested-by: Pedro Falcato --- include/linux/mm.h | 3 +-- mm/mmap.c | 6 ------ mm/nommu.c | 5 ----- 3 files changed, 1 insertion(+), 13 deletions(-) diff --git a/include/linux/mm.h b/include/linux/mm.h index bf5d0b1b16f4..216dd0c6dcf8 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3308,8 +3308,7 @@ static inline void mm_populate(unsigned long addr, un= signed long len) static inline void mm_populate(unsigned long addr, unsigned long len) {} #endif =20 -/* These take the mm semaphore themselves */ -extern int __must_check vm_brk(unsigned long, unsigned long); +/* This takes the mm semaphore itself */ extern int __must_check vm_brk_flags(unsigned long, unsigned long, unsigne= d long); extern int vm_munmap(unsigned long, size_t); extern unsigned long __must_check vm_mmap(struct file *, unsigned long, diff --git a/mm/mmap.c b/mm/mmap.c index b56a7f0c9f85..34d2337ace59 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -3174,12 +3174,6 @@ int vm_brk_flags(unsigned long addr, unsigned long r= equest, unsigned long flags) } EXPORT_SYMBOL(vm_brk_flags); =20 -int vm_brk(unsigned long addr, unsigned long len) -{ - return vm_brk_flags(addr, len, 0); -} -EXPORT_SYMBOL(vm_brk); - /* Release all mmaps. */ void exit_mmap(struct mm_struct *mm) { diff --git a/mm/nommu.c b/mm/nommu.c index 7f9e9e5a0e12..23c43c208f2b 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1531,11 +1531,6 @@ void exit_mmap(struct mm_struct *mm) mmap_write_unlock(mm); } =20 -int vm_brk(unsigned long addr, unsigned long len) -{ - return -ENOMEM; -} - /* * expand (or shrink) an existing mapping, potentially moving it at the sa= me * time (controlled by the MREMAP_MAYMOVE flag and available VM space) --=20 2.34.1