From nobody Fri Apr 3 08:01:28 2026 Received: from mail-oo1-f74.google.com (mail-oo1-f74.google.com [209.85.161.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 458682BD01B for ; Tue, 17 Feb 2026 18:01:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.74 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771351276; cv=none; b=sEsekfUg9KOjiO1UhqplfZZGLHWkEqYZrfDWt+Ktnh/asPKRGu6uH0SMZ/P3vuzV0TjBwbuYXxuwGSAU04TBDLqHHz4oq/gX+6JYrm3f9F/BRX9FNjo6ugQEkHfPbY6AZ+SEe5kJE88c0289Y+o93/4Zb1THprEqfUXoUIiRzHY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771351276; c=relaxed/simple; bh=IMo7fTZiH5AjbqIlP1FpJeao4rQ8mb0ZRSl0gCTzrco=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Li0W1dr5MW642BEOEYYnWrILodR7MqAm7CTpXDNqkksaXiAqlMhA9XtBPKTcWjkK1PBRGPVawLlpJX54AmyLhUUS1zrqs3YyOgTJuSvLZS+DDd9SovJTBOZNUGtPkeKSL8dTIVOuHFEw9vQKWvpdYD3RPp0cbP3umxPt+Evrmvo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--avagin.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=cBScIjuJ; arc=none smtp.client-ip=209.85.161.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--avagin.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="cBScIjuJ" Received: by mail-oo1-f74.google.com with SMTP id 006d021491bc7-678f3fef828so45048488eaf.1 for ; Tue, 17 Feb 2026 10:01:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1771351274; x=1771956074; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=zNf1st2FT2PYXwVv7YSArpm+3hAEziPMQnbmcsUNwA8=; b=cBScIjuJbSK0MAIIJ0IkAAfG4mzSLTMKibqW8EV8CDg2m4WqplDlgQMpIenXC2u5PK 8TsQgBGHMjfXZKjPxTWsfAgU9gxpRefyMbU3uoN7PENBINz9RZsuoSLJMa9I8IgfvFrR 1lE6h/i4Is4BVMNbL5R3vkQGNo5uYeMQTzY6pwtIUubtYQLBTBnSHI4QNUdaBQqEKf19 rieZJqV+tdH+j6u1tGedpSIu6w0KgbbZWfIOMDuYbyEK9WX/J+9aqJ5NuoF3hKQxVEgw IR6Ingz6krSB54x2F+FoxTe85Df9Bjs162g8KpnIEoHCl7MK1RyL+pPbrM7lCfOoRGBB QtoA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771351274; x=1771956074; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=zNf1st2FT2PYXwVv7YSArpm+3hAEziPMQnbmcsUNwA8=; b=t62iXTZz7CTfQXRCwebaPyApgqEM8aK6eb0lcTV0DGB+mGN+YGBcuxgI2rqy/TYnqL rvCcBcs33fITwumtszVfGUKMp+VfI/T/hzUwfFtj+DBnfvwrC1Pln968qXM0XTkg09ce iWTnAclkb0VnPLS5YUHPuQmLka0vcxeIEkQ3kYcmywlmrFli6h8q/odzuS8h9pP/acYb o/x2nA7cAuAVp9D4GNEq3cc4Ld37l4hrbdzVqRiS83KkGj0vOEz0qothzVN1pdXkglLA wnbmjAVX+UX7YWwO7xQCDuqnOCbWC9nV+i9wrls6iPm2SRaqY5HyoXcjfm6uxOOwPKX1 vriQ== X-Forwarded-Encrypted: i=1; AJvYcCW+hagoXPfPYjNEceS1IoamS+hWJvI2WhzDTYYybn+g/o1+HvKY5QhbojJalOs4HoyJvePJP76qqZ05AYU=@vger.kernel.org X-Gm-Message-State: AOJu0YwyrsQrp3WFQhF0kzTS4EmfIEtx3cV0zNtJ+jz11S/qh++0o4dx b5i6xd1MggvvDlDO8lvWZ4Gv5iJzuwd55OJfybEEGBy8Benckz0HAqQ89pT0CdcGrVrnDObQZB0 ki2IC9Q== X-Received: from jabx17.prod.google.com ([2002:a02:6f11:0:b0:5cf:13a7:b8e8]) (user=avagin job=prod-delivery.src-stubby-dispatcher) by 2002:a4a:e719:0:b0:678:cf78:1e9a with SMTP id 006d021491bc7-678cf7820e5mr4561614eaf.35.1771351274078; Tue, 17 Feb 2026 10:01:14 -0800 (PST) Date: Tue, 17 Feb 2026 18:01:06 +0000 In-Reply-To: <20260217180108.1420024-1-avagin@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260217180108.1420024-1-avagin@google.com> X-Mailer: git-send-email 2.53.0.310.g728cabbaf7-goog Message-ID: <20260217180108.1420024-3-avagin@google.com> Subject: [PATCH 2/4] exec: inherit HWCAPs from the parent process From: Andrei Vagin To: Kees Cook , Andrew Morton Cc: Cyrill Gorcunov , Mike Rapoport , Alexander Mikhalitsyn , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, criu@lists.linux.dev, Chen Ridong , Christian Brauner , David Hildenbrand , Eric Biederman , Lorenzo Stoakes , Michal Koutny , Andrei Vagin , Alexander Mikhalitsyn Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Introduces a mechanism to inherit hardware capabilities (AT_HWCAP, AT_HWCAP2, etc.) from a parent process when they have been modified via prctl. To support C/R operations (snapshots, live migration) in heterogeneous clusters, we must ensure that processes utilize CPU features available on all potential target nodes. To solve this, we need to advertise a common feature set across the cluster. This patch adds a new mm flag MMF_USER_HWCAP, which is set when the auxiliary vector is modified via prctl(PR_SET_MM, PR_SET_MM_AUXV). When execve() is called, if the current process has MMF_USER_HWCAP set, the HWCAP values are extracted from the current auxiliary vector and stored in the linux_binprm structure. These values are then used to populate the auxiliary vector of the new process, effectively inheriting the hardware capabilities. The inherited HWCAPs are masked with the hardware capabilities supported by the current kernel to ensure that we don't report more features than actually supported. This is important to avoid unexpected behavior, especially for processes with additional privileges. Reviewed-by: Cyrill Gorcunov Reviewed-by: Alexander Mikhalitsyn Signed-off-by: Andrei Vagin --- fs/binfmt_elf.c | 8 ++--- fs/binfmt_elf_fdpic.c | 8 ++--- fs/exec.c | 63 ++++++++++++++++++++++++++++++++++++++++ include/linux/binfmts.h | 11 +++++++ include/linux/mm_types.h | 2 ++ kernel/fork.c | 3 ++ kernel/sys.c | 5 +++- 7 files changed, 91 insertions(+), 9 deletions(-) diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index 3eb734c192e9..aec129e33f0b 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -246,7 +246,7 @@ create_elf_tables(struct linux_binprm *bprm, const stru= ct elfhdr *exec, */ ARCH_DLINFO; #endif - NEW_AUX_ENT(AT_HWCAP, ELF_HWCAP); + NEW_AUX_ENT(AT_HWCAP, bprm->hwcap); NEW_AUX_ENT(AT_PAGESZ, ELF_EXEC_PAGESIZE); NEW_AUX_ENT(AT_CLKTCK, CLOCKS_PER_SEC); NEW_AUX_ENT(AT_PHDR, phdr_addr); @@ -264,13 +264,13 @@ create_elf_tables(struct linux_binprm *bprm, const st= ruct elfhdr *exec, NEW_AUX_ENT(AT_SECURE, bprm->secureexec); NEW_AUX_ENT(AT_RANDOM, (elf_addr_t)(unsigned long)u_rand_bytes); #ifdef ELF_HWCAP2 - NEW_AUX_ENT(AT_HWCAP2, ELF_HWCAP2); + NEW_AUX_ENT(AT_HWCAP2, bprm->hwcap2); #endif #ifdef ELF_HWCAP3 - NEW_AUX_ENT(AT_HWCAP3, ELF_HWCAP3); + NEW_AUX_ENT(AT_HWCAP3, bprm->hwcap3); #endif #ifdef ELF_HWCAP4 - NEW_AUX_ENT(AT_HWCAP4, ELF_HWCAP4); + NEW_AUX_ENT(AT_HWCAP4, bprm->hwcap4); #endif NEW_AUX_ENT(AT_EXECFN, bprm->exec); if (k_platform) { diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index a3d4e6973b29..55b482f03c82 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -629,15 +629,15 @@ static int create_elf_fdpic_tables(struct linux_binpr= m *bprm, */ ARCH_DLINFO; #endif - NEW_AUX_ENT(AT_HWCAP, ELF_HWCAP); + NEW_AUX_ENT(AT_HWCAP, bprm->hwcap); #ifdef ELF_HWCAP2 - NEW_AUX_ENT(AT_HWCAP2, ELF_HWCAP2); + NEW_AUX_ENT(AT_HWCAP2, bprm->hwcap2); #endif #ifdef ELF_HWCAP3 - NEW_AUX_ENT(AT_HWCAP3, ELF_HWCAP3); + NEW_AUX_ENT(AT_HWCAP3, bprm->hwcap3); #endif #ifdef ELF_HWCAP4 - NEW_AUX_ENT(AT_HWCAP4, ELF_HWCAP4); + NEW_AUX_ENT(AT_HWCAP4, bprm->hwcap4); #endif NEW_AUX_ENT(AT_PAGESZ, PAGE_SIZE); NEW_AUX_ENT(AT_CLKTCK, CLOCKS_PER_SEC); diff --git a/fs/exec.c b/fs/exec.c index 2e3a6593c6fd..9c70776fca9e 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1454,6 +1454,17 @@ static struct linux_binprm *alloc_bprm(int fd, struc= t filename *filename, int fl */ bprm->is_check =3D !!(flags & AT_EXECVE_CHECK); =20 + bprm->hwcap =3D ELF_HWCAP; +#ifdef ELF_HWCAP2 + bprm->hwcap2 =3D ELF_HWCAP2; +#endif +#ifdef ELF_HWCAP3 + bprm->hwcap3 =3D ELF_HWCAP3; +#endif +#ifdef ELF_HWCAP4 + bprm->hwcap4 =3D ELF_HWCAP4; +#endif + retval =3D bprm_mm_init(bprm); if (!retval) return bprm; @@ -1775,6 +1786,55 @@ static int bprm_execve(struct linux_binprm *bprm) return retval; } =20 +static void inherit_hwcap(struct linux_binprm *bprm) +{ + struct mm_struct *mm =3D current->mm; + int i, n; + +#ifdef ELF_HWCAP4 + n =3D 4; +#elif defined(ELF_HWCAP3) + n =3D 3; +#elif defined(ELF_HWCAP2) + n =3D 2; +#else + n =3D 1; +#endif + + for (i =3D 0; n && i < AT_VECTOR_SIZE; i +=3D 2) { + unsigned long type =3D mm->saved_auxv[i]; + unsigned long val =3D mm->saved_auxv[i + 1]; + + switch (type) { + case AT_NULL: + goto done; + case AT_HWCAP: + bprm->hwcap =3D val & ELF_HWCAP; + break; +#ifdef ELF_HWCAP2 + case AT_HWCAP2: + bprm->hwcap2 =3D val & ELF_HWCAP2; + break; +#endif +#ifdef ELF_HWCAP3 + case AT_HWCAP3: + bprm->hwcap3 =3D val & ELF_HWCAP3; + break; +#endif +#ifdef ELF_HWCAP4 + case AT_HWCAP4: + bprm->hwcap4 =3D val & ELF_HWCAP4; + break; +#endif + default: + continue; + } + n--; + } +done: + mm_flags_set(MMF_USER_HWCAP, bprm->mm); +} + static int do_execveat_common(int fd, struct filename *filename, struct user_arg_ptr argv, struct user_arg_ptr envp, @@ -1843,6 +1903,9 @@ static int do_execveat_common(int fd, struct filename= *filename, current->comm, bprm->filename); } =20 + if (mm_flags_test(MMF_USER_HWCAP, current->mm)) + inherit_hwcap(bprm); + return bprm_execve(bprm); } =20 diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h index 65abd5ab8836..94a3dcf9b1d2 100644 --- a/include/linux/binfmts.h +++ b/include/linux/binfmts.h @@ -2,6 +2,7 @@ #ifndef _LINUX_BINFMTS_H #define _LINUX_BINFMTS_H =20 +#include #include #include #include @@ -67,6 +68,16 @@ struct linux_binprm { unsigned long exec; =20 struct rlimit rlim_stack; /* Saved RLIMIT_STACK used during exec. */ + unsigned long hwcap; +#ifdef ELF_HWCAP2 + unsigned long hwcap2; +#endif +#ifdef ELF_HWCAP3 + unsigned long hwcap3; +#endif +#ifdef ELF_HWCAP4 + unsigned long hwcap4; +#endif =20 char buf[BINPRM_BUF_SIZE]; } __randomize_layout; diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 8731606d8d36..2f3c6ad48c0a 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1918,6 +1918,8 @@ enum { #define MMF_TOPDOWN 31 /* mm searches top down by default */ #define MMF_TOPDOWN_MASK BIT(MMF_TOPDOWN) =20 +#define MMF_USER_HWCAP 32 /* user-defined HWCAPs */ + #define MMF_INIT_LEGACY_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\ MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK |\ MMF_VM_MERGE_ANY_MASK | MMF_TOPDOWN_MASK) diff --git a/kernel/fork.c b/kernel/fork.c index e832da9d15a4..4c92a2bc3cbb 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1104,6 +1104,9 @@ static struct mm_struct *mm_init(struct mm_struct *mm= , struct task_struct *p, =20 __mm_flags_overwrite_word(mm, mmf_init_legacy_flags(flags)); mm->def_flags =3D current->mm->def_flags & VM_INIT_DEF_MASK; + + if (mm_flags_test(MMF_USER_HWCAP, current->mm)) + mm_flags_set(MMF_USER_HWCAP, mm); } else { __mm_flags_overwrite_word(mm, default_dump_filter); mm->def_flags =3D 0; diff --git a/kernel/sys.c b/kernel/sys.c index cdbf8513caf6..e4b0fa2f6845 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2157,8 +2157,10 @@ static int prctl_set_mm_map(int opt, const void __us= er *addr, unsigned long data * not introduce additional locks here making the kernel * more complex. */ - if (prctl_map.auxv_size) + if (prctl_map.auxv_size) { memcpy(mm->saved_auxv, user_auxv, sizeof(user_auxv)); + mm_flags_set(MMF_USER_HWCAP, mm); + } =20 mmap_read_unlock(mm); return 0; @@ -2190,6 +2192,7 @@ static int prctl_set_auxv(struct mm_struct *mm, unsig= ned long addr, =20 task_lock(current); memcpy(mm->saved_auxv, user_auxv, len); + mm_flags_set(MMF_USER_HWCAP, mm); task_unlock(current); =20 return 0; --=20 2.53.0.310.g728cabbaf7-goog