From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 F017642BC42; Fri, 7 Aug 2026 15:15:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786115714; cv=none; b=syNVx+Kztip8PS5eXZ5DOM0XVf4Qm8P4h8NwGlpTzM9wiynCg/hBueBES09Hs87s2SOVYNmtZcF5G9weZkjgB4CvFmPqdceJex7W2zfH9Gyp1wZBu+ICmKLkv6+lOsWFccdUy1KzhR/fC4XRof5BfAsMRgMm6AQ9zcja2i2M/wI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786115714; c=relaxed/simple; bh=zDRb8T6CefX0vwxBwM2goC5xV4heM3DoD89uKVThBRk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ah9z7fcX7sHLkXJVskynDVdttFrlD6WOEVvGFCJB0BkKAa6mRgoxnHvcptBEvGCusjjG+dURWDmykYYAWrrTpMGaCoKFCh8nY3+RfJn7sIeu58FBm1bGDGP/U/uo2y4Vsu1Ew/b3oQXZDXRkS5h6t+BhFdrg041IjpCeAORmKwc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=LO+jLRjZ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="LO+jLRjZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4A5DD1F000E9; Fri, 7 Aug 2026 15:15:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786115712; bh=Vgi5dRwSdqt8reOsZ7THRi6CiAXXaTcaRq4Ejmm8HRM=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=LO+jLRjZOodZUs4ch2159xKziud46botQ0+lisEGbkGrYmc82M06sy/XWicItNYxq o7n/wq4ex/ZP/1tdzHhySK4a0g32StQ1U0qSk4Ew2rf8ns5+lv7ObboRPpmKWGw+ml Snzhwok8Iz6YmFYWeo6TJRlC74vKhFl1/ONtZRHo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Mike Rapoport (Microsoft)" , vova tokarev , "David Hildenbrand (Arm)" , Lorenzo Stoakes , Al Viro , Christian Brauner , Jan Kara , Linus Torvalds , Oleg Nesterov , Peter Xu , Andrew Morton , Sasha Levin Subject: [PATCH 6.18 371/396] userfaultfd: prevent registration of special VMAs Date: Fri, 7 Aug 2026 16:38:51 +0200 Message-ID: <20260807143432.284246423@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260807143424.272339768@linuxfoundation.org> References: <20260807143424.272339768@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Mike Rapoport (Microsoft)" [ Upstream commit 3c58f641e813c3c71039f8fd4d4e2a3aab713288 ] Vova Tokarev says: userfaultfd allows registration on shadow stack VMAs. With userfaultfd access, you can register on the shadow stack, discard a page ... and inject a page with chosen return addresses via UFFDIO_COPY. Update vma_can_userfault() to reject VM_SHADOW_STACK. While on it, also reject VM_SPECIAL so that if a driver would implement vm_uffd_ops, it wouldn't be possible to register special VMAs with userfaultfd. Since VM_SPECIAL includes VM_DONTEXPAND which is set but hugetlb, exclude hugetlb VMAs from the check for VM_SPECIAL. Link: https://lore.kernel.org/20260618095017.2553004-1-rppt@kernel.org Fixes: 54007f818206 ("mm: Introduce VM_SHADOW_STACK for shadow stack memory") Signed-off-by: Mike Rapoport (Microsoft) Reported-by: vova tokarev Acked-by: David Hildenbrand (Arm) Reviewed-by: Lorenzo Stoakes Cc: Al Viro Cc: Christian Brauner Cc: Jan Kara Cc: Linus Torvalds Cc: Mike Rapoport Cc: Oleg Nesterov Cc: Peter Xu Cc: Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- include/linux/userfaultfd_k.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- a/include/linux/userfaultfd_k.h +++ b/include/linux/userfaultfd_k.h @@ -214,7 +214,10 @@ static inline bool vma_can_userfault(str { vm_flags &= __VM_UFFD_FLAGS; - if (vma->vm_flags & VM_DROPPABLE) + if (vma->vm_flags & (VM_DROPPABLE | VM_SHADOW_STACK)) + return false; + + if (!is_vm_hugetlb_page(vma) && (vma->vm_flags & VM_SPECIAL)) return false; if ((vm_flags & VM_UFFD_MINOR) &&