From nobody Wed Apr 8 00:00:01 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 4B3E8C4332F for ; Thu, 20 Oct 2022 23:17:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229652AbiJTXRt (ORCPT ); Thu, 20 Oct 2022 19:17:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230148AbiJTXRk (ORCPT ); Thu, 20 Oct 2022 19:17:40 -0400 Received: from mail-ua1-x935.google.com (mail-ua1-x935.google.com [IPv6:2607:f8b0:4864:20::935]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 76D4E22EE37 for ; Thu, 20 Oct 2022 16:17:35 -0700 (PDT) Received: by mail-ua1-x935.google.com with SMTP id t26so1183186uaj.9 for ; Thu, 20 Oct 2022 16:17:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=C+z4UK+YSd44EWa9tT929JkG3rIhRX9wOtAF4K/xipQ=; b=Fz+yVYwnrjHx4w+MtD2CSa58RDIbjKnPExtdGatd7EutqG2N4rAwQDm7iMBlBm+zsI 3hJdP9a62OXzPjOCb9DIYZs8ef0ybSyRf1qFHBBKe9gN3VwpddxGIF+iY6ifJZIKObqW mlaBZ/91X4IcOnT3pWS/wbjoi2xAcyZkIh9bZeupDqa48pyQ3c/O1v+DAJaLtVmG/pPW 8rIxSST0Ya3NM3a+ACBfI0LaZY6TOFdr2Lo4k+zGAAfAOyZxR19Ts+JGRHc/SVAT6Noo e1h6g/XvjGpDF8hB/fIitRw4xKIMTr86OLyzavnTsQ+pL9lVsAuiIpX+V7APEP/zUONj NjsQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=C+z4UK+YSd44EWa9tT929JkG3rIhRX9wOtAF4K/xipQ=; b=o/A+t9LLbtQlxhSmp9T6lb0LZj9iJS8ZF0c0iJuSXgMA/PvbNhkLcv9IzR+qpNqArc 8zflIKWUwMituWtON2KCn+DeUUaKv3Uv5XX8uwpHPeg79cr5h0PO7G9tSKssReHDFH7/ glODObUpJdd5Gnh2IZpW9/qFMsY4OOEWd5ha4EwTHYnB7um2W32yYjPYRpJbDzBW/nLm 17+0MtN/rG9082960QEHYHWDnB9dOsSWd24EDsL/+JU3bBbwNrSsy4lfRBE8UeIO/nRo gfFrOxBc1mzI7/QycJxO3dhu5f/EavZgdpHNq2JdCYIJKB2XIEION5Q4qTVUd79NJcLz WMBw== X-Gm-Message-State: ACrzQf00cUQkQzgUuFbUwWSrkImDkpjvUTZoGs0vgRs7QR4gQjpOa/iO Nz4N+TIDnOw3mQxvuNmqY8bpTIbvex96+Fb+3q8= X-Google-Smtp-Source: AMsMyM7YzZwl3myeXX3Vw+eUWCO1XEA3766+HOJj4kxM1O9KV2vKo2LYx9EacG1cGuYvJFoPJGvr7w== X-Received: by 2002:a17:902:e5d1:b0:183:b450:ef76 with SMTP id u17-20020a170902e5d100b00183b450ef76mr16122080plf.151.1666307843787; Thu, 20 Oct 2022 16:17:23 -0700 (PDT) Received: from localhost ([183.242.254.175]) by smtp.gmail.com with ESMTPSA id b3-20020a17090a990300b0020b2082e0acsm384222pjp.0.2022.10.20.16.17.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 20 Oct 2022 16:17:23 -0700 (PDT) From: Hawkins Jiawei To: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com, Mike Kravetz , Muchun Song Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, 18801353760@163.com, yin31149@gmail.com Subject: [PATCH -next] hugetlbfs: fix null-ptr-deref in hugetlbfs_parse_param() Date: Fri, 21 Oct 2022 07:16:08 +0800 Message-Id: <20221020231609.4810-1-yin31149@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Syzkaller reports a null-ptr-deref bug as follows: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: 0010:hugetlbfs_parse_param+0x1dd/0x8e0 fs/hugetlbfs/inode.c:1380 [...] Call Trace: vfs_parse_fs_param fs/fs_context.c:148 [inline] vfs_parse_fs_param+0x1f9/0x3c0 fs/fs_context.c:129 vfs_parse_fs_string+0xdb/0x170 fs/fs_context.c:191 generic_parse_monolithic+0x16f/0x1f0 fs/fs_context.c:231 do_new_mount fs/namespace.c:3036 [inline] path_mount+0x12de/0x1e20 fs/namespace.c:3370 do_mount fs/namespace.c:3383 [inline] __do_sys_mount fs/namespace.c:3591 [inline] __se_sys_mount fs/namespace.c:3568 [inline] __x64_sys_mount+0x27f/0x300 fs/namespace.c:3568 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd [...] =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D According to commit ac369cdd9448("vfs: parse: deal with zero length string value"), kernel will sets the param->string to null pointer in vfs_parse_fs_string() if fs string has zero length. Yet the problem is that, hugetlbfs_parse_param() will dereference the param->string, without checking whether it is a null pointer. To be more specific, if hugetlbfs_parse_param() parses an illegal mount parameter, such as "size=3D,", kernel will constructs struct fs_parameter with null pointer in vfs_parse_fs_string(), then passes this struct fs_parameter to hugetlbfs_parse_param(), which triggers the above null-ptr-deref bug. This patch solves it by adding sanity check on param->string in hugetlbfs_parse_param(). Reported-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com Tested-by: syzbot+a3e6acd85ded5c16a709@syzkaller.appspotmail.com Link: https://lore.kernel.org/all/0000000000005ad00405eb7148c6@google.com/ Signed-off-by: Hawkins Jiawei Reviewed-by: Mike Kravetz --- fs/hugetlbfs/inode.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 7f836f8f9db1..3ee84604e36d 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -1377,7 +1377,7 @@ static int hugetlbfs_parse_param(struct fs_context *f= c, struct fs_parameter *par =20 case Opt_size: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->max_size_opt =3D memparse(param->string, &rest); ctx->max_val_type =3D SIZE_STD; @@ -1387,7 +1387,7 @@ static int hugetlbfs_parse_param(struct fs_context *f= c, struct fs_parameter *par =20 case Opt_nr_inodes: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->nr_inodes =3D memparse(param->string, &rest); return 0; @@ -1403,7 +1403,7 @@ static int hugetlbfs_parse_param(struct fs_context *f= c, struct fs_parameter *par =20 case Opt_min_size: /* memparse() will accept a K/M/G without a digit */ - if (!isdigit(param->string[0])) + if (!param->string || !isdigit(param->string[0])) goto bad_val; ctx->min_size_opt =3D memparse(param->string, &rest); ctx->min_val_type =3D SIZE_STD; --=20 2.25.1