From nobody Sat Feb 7 22:07:09 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2AB9913A244; Sat, 26 Apr 2025 00:11:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745626283; cv=none; b=WdgcExRY9yokFhqTtN4kGEJP6czhHRja/db8VzgzJCBkImaUxhelx58UNn9UNJH4pXUcJNMBRlo92eb0sIogs3wOr3vhdDMn78n7/aGBNz35k/NGUOsBgT37NG0eu1n0AXI9jKX+XBLpTO2nNtszS5Cjt+cS7IOVm1nVEeypPpg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745626283; c=relaxed/simple; bh=DFNipnoqmsR5fihOyPm8o+8H9EYU2K0QxreJWh7S2IU=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=MvEX5ou1MlLeO//RCFv8ROcmrcMwX02MaCOanadFZk7/VpIyVmzZ1+koYK5ZTx9s2AmRNO/QHhq9G8JUFQZPcrQNAHGeQGJ6ka/G18rdFPglPt1nNPLADb5xCLTeiFJyx+P936GH60OkVefFfrCglRAAX+R73Gjm1Cupp1IriBA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WgIq0piQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WgIq0piQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7E672C4CEE4; Sat, 26 Apr 2025 00:11:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1745626282; bh=DFNipnoqmsR5fihOyPm8o+8H9EYU2K0QxreJWh7S2IU=; h=From:To:Cc:Subject:Date:From; b=WgIq0piQPB32xXyAho4BKC8PU4ny3GmB6xplNbn6HMbs1bPzGdu99PZdxqK0EKahj enZSTa/WInTc6O5uARi/BCiVMry2bA6vYt2ZZwBYmjLXkqQuF/ycwKsVnPKehLAINO IfkwPHGpzlDXBDHkPTY/zWY7T2SPZGxiftPYrxuQpE5vNa/m6PDAZdq1Ahz74Edjgj 4VsvkHUW+svDuOYqup//vYx6FhLkt3sfbxNRP375+hkxVvfIZTirxVz17vmmVzyQTx mEKOkEIOzZsUNh8sOzf3ZsLfkFXLEWcikRQoWyeBeqGTXtmtZWGYrRobI87WeeA8w+ Rg3hAmQTpj/HA== From: Kees Cook To: Andrew Morton Cc: Kees Cook , Erhard Furtner , Danilo Krummrich , Michal Hocko , Vlastimil Babka , Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH v2] mm: vmalloc: Support more granular vrealloc() sizing Date: Fri, 25 Apr 2025 17:11:07 -0700 Message-Id: <20250426001105.it.679-kees@kernel.org> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3832; i=kees@kernel.org; h=from:subject:message-id; bh=DFNipnoqmsR5fihOyPm8o+8H9EYU2K0QxreJWh7S2IU=; b=owGbwMvMwCVmps19z/KJym7G02pJDBk8KrMa8utO1i8SvnOyNfzJwpStsSc+S6xfEHJq4puwp awzvl/m6ChlYRDjYpAVU2QJsnOPc/F42x7uPlcRZg4rE8gQBi5OAZjIx8WMDO1H2qZ43jOfe+fV ahXXxJQTxdtvXN8j8bCzZVHbx/+5K/8zMjw4eTmkufjmp4aFrLfa3n1U/+T2dbFQ8b6vbgdd1m1 pWccBAA== X-Developer-Key: i=kees@kernel.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Introduce struct vm_struct::requested_size so that the requested (re)allocation size is retained separately from the allocated area size. This means that KASAN will correctly poison the correct spans of requested bytes. This also means we can support growing the usable portion of an allocation that can already be supported by the existing area's existing allocation. Reported-by: Erhard Furtner Closes: https://lore.kernel.org/all/20250408192503.6149a816@outsider.home/ Fixes: 3ddc2fefe6f3 ("mm: vmalloc: implement vrealloc()") Signed-off-by: Kees Cook Reviewed-by: Danilo Krummrich --- Cc: Andrew Morton Cc: Danilo Krummrich Cc: Michal Hocko Cc: Vlastimil Babka Cc: Uladzislau Rezki Cc: --- include/linux/vmalloc.h | 1 + mm/vmalloc.c | 31 ++++++++++++++++++++++++------- 2 files changed, 25 insertions(+), 7 deletions(-) diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h index 31e9ffd936e3..5ca8d4dd149d 100644 --- a/include/linux/vmalloc.h +++ b/include/linux/vmalloc.h @@ -61,6 +61,7 @@ struct vm_struct { unsigned int nr_pages; phys_addr_t phys_addr; const void *caller; + unsigned long requested_size; }; =20 struct vmap_area { diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 3ed720a787ec..2d7511654831 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -1940,7 +1940,7 @@ static inline void setup_vmalloc_vm(struct vm_struct = *vm, { vm->flags =3D flags; vm->addr =3D (void *)va->va_start; - vm->size =3D va_size(va); + vm->size =3D vm->requested_size =3D va_size(va); vm->caller =3D caller; va->vm =3D vm; } @@ -3133,6 +3133,7 @@ struct vm_struct *__get_vm_area_node(unsigned long si= ze, =20 area->flags =3D flags; area->caller =3D caller; + area->requested_size =3D requested_size; =20 va =3D alloc_vmap_area(size, align, start, end, node, gfp_mask, 0, area); if (IS_ERR(va)) { @@ -4063,6 +4064,8 @@ EXPORT_SYMBOL(vzalloc_node_noprof); */ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags) { + struct vm_struct *vm =3D NULL; + size_t alloced_size =3D 0; size_t old_size =3D 0; void *n; =20 @@ -4072,15 +4075,17 @@ void *vrealloc_noprof(const void *p, size_t size, g= fp_t flags) } =20 if (p) { - struct vm_struct *vm; - vm =3D find_vm_area(p); if (unlikely(!vm)) { WARN(1, "Trying to vrealloc() nonexistent vm area (%p)\n", p); return NULL; } =20 - old_size =3D get_vm_area_size(vm); + alloced_size =3D get_vm_area_size(vm); + old_size =3D vm->requested_size; + if (WARN(alloced_size < old_size, + "vrealloc() has mismatched area vs requested sizes (%p)\n", p)) + return NULL; } =20 /* @@ -4088,14 +4093,26 @@ void *vrealloc_noprof(const void *p, size_t size, g= fp_t flags) * would be a good heuristic for when to shrink the vm_area? */ if (size <=3D old_size) { - /* Zero out spare memory. */ - if (want_init_on_alloc(flags)) + /* Zero out "freed" memory. */ + if (want_init_on_free()) memset((void *)p + size, 0, old_size - size); + vm->requested_size =3D size; kasan_poison_vmalloc(p + size, old_size - size); - kasan_unpoison_vmalloc(p, size, KASAN_VMALLOC_PROT_NORMAL); return (void *)p; } =20 + /* + * We already have the bytes available in the allocation; use them. + */ + if (size <=3D alloced_size) { + kasan_unpoison_vmalloc(p + old_size, size - old_size, + KASAN_VMALLOC_PROT_NORMAL); + /* Zero out "alloced" memory. */ + if (want_init_on_alloc(flags)) + memset((void *)p + old_size, 0, size - old_size); + vm->requested_size =3D size; + } + /* TODO: Grow the vm_area, i.e. allocate and map additional pages. */ n =3D __vmalloc_noprof(size, flags); if (!n) --=20 2.34.1