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 26BBB3D810C; Tue, 16 Jun 2026 18:27:15 +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=1781634436; cv=none; b=bOGsj8Ez7J+/GOUHLyy+CWMlvpvtdxHXOmoKLPIk1MywB2gigoHQ/SvPWZZNWoRyUn6fx5XkZ1S37iWM5tlNfqTgfJWXOVkSpikXCQCq/1jQoIefkwvVkaQCF7tbdHf6ptX2u/alnUUsNWBnFdjV5CiXXooEIeA5zqIYUmi2VmM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781634436; c=relaxed/simple; bh=wNATrmJ1u1J+Y7NgUf/bIl+GJyT9QFAVNCjOc9BmzvA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=tLvnuMkAAUyNXGhMrKgoiimVKcZhT4cbKIGOD7f8YGrH+4rsov9xrlNab62McSgBpPViMep03cL33Lalyl06QJEm/cpOfDoQduqmp/7/0oZqcHdR3YvqDJiIr17LiXIs7kRPFJWjh5ff4R9xAXaDyJvS49xvpc3+IiyuqQKHTLw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JjMummUa; 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="JjMummUa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 301471F000E9; Tue, 16 Jun 2026 18:27:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781634435; bh=JQO1AFkkhWijLPjMns4IyiH0ZfFtpIm4d9NuzVywyL0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=JjMummUaAjZxmajN0sv3vkgL8N3lf0FBBG5hJ32rnWiNnHcIMr2cpKIJJiIUw6gUf vA8zkWKLAz4pqJKdXCoNFy5LTKsOYaf98aUeMGmcq8tOujMA1da9kPR5JMIinO7KrW bwcieaL+oRFXGAeTG5UthDvJhOIK5dQYwaA+96Ns= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Michael Bommarito , Namjae Jeon , Steve French , Sasha Levin Subject: [PATCH 5.15 257/411] ksmbd: require minimum ACE size in smb_check_perm_dacl() Date: Tue, 16 Jun 2026 20:28:15 +0530 Message-ID: <20260616145114.656367555@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260616145100.376842714@linuxfoundation.org> References: <20260616145100.376842714@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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michael Bommarito [ Upstream commit d07b26f39246a82399661936dd0c853983cfade7 ] Both ACE-walk loops in smb_check_perm_dacl() only guard against an under-sized remaining buffer, not against an ACE whose declared `ace->size` is smaller than the struct it claims to describe: if (offsetof(struct smb_ace, access_req) > aces_size) break; ace_size = le16_to_cpu(ace->size); if (ace_size > aces_size) break; The first check only requires the 4-byte ACE header to be in bounds; it does not require access_req (4 bytes at offset 4) to be readable. An attacker who has set a crafted DACL on a file they own can declare ace->size == 4 with aces_size == 4, pass both checks, and then granted |= le32_to_cpu(ace->access_req); /* upper loop */ compare_sids(&sid, &ace->sid); /* lower loop */ reads access_req at offset 4 (OOB by up to 4 bytes) and ace->sid at offset 8 (OOB by up to CIFS_SID_BASE_SIZE + SID_MAX_SUB_AUTHORITIES * 4 bytes). Tighten both loops to require ace_size >= offsetof(struct smb_ace, sid) + CIFS_SID_BASE_SIZE which is the smallest valid on-wire ACE layout (4-byte header + 4-byte access_req + 8-byte sid base with zero sub-auths). Also reject ACEs whose sid.num_subauth exceeds SID_MAX_SUB_AUTHORITIES before letting compare_sids() dereference sub_auth[] entries. parse_sec_desc() already enforces an equivalent check (lines 441-448); smb_check_perm_dacl() simply grew weaker validation over time. Reachability: authenticated SMB client with permission to set an ACL on a file. On a subsequent CREATE against that file, the kernel walks the stored DACL via smb_check_perm_dacl() and triggers the OOB read. Not pre-auth, and the OOB read is not reflected to the attacker, but KASAN reports and kernel state corruption are possible. Fixes: e2f34481b24d ("cifsd: add server-side procedures for SMB3") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Assisted-by: Codex:gpt-5-4 Signed-off-by: Michael Bommarito Acked-by: Namjae Jeon Signed-off-by: Steve French [ changed le16_to_cpu to le32_to_cpu for num_aces field which is __le32 ] Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- fs/ksmbd/smbacl.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) --- a/fs/ksmbd/smbacl.c +++ b/fs/ksmbd/smbacl.c @@ -1265,10 +1265,13 @@ int smb_check_perm_dacl(struct ksmbd_con ace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl)); aces_size = acl_size - sizeof(struct smb_acl); for (i = 0; i < le32_to_cpu(pdacl->num_aces); i++) { - if (offsetof(struct smb_ace, access_req) > aces_size) + if (offsetof(struct smb_ace, sid) + + aces_size < CIFS_SID_BASE_SIZE) break; ace_size = le16_to_cpu(ace->size); - if (ace_size > aces_size) + if (ace_size > aces_size || + ace_size < offsetof(struct smb_ace, sid) + + CIFS_SID_BASE_SIZE) break; aces_size -= ace_size; granted |= le32_to_cpu(ace->access_req); @@ -1286,13 +1289,19 @@ int smb_check_perm_dacl(struct ksmbd_con ace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl)); aces_size = acl_size - sizeof(struct smb_acl); for (i = 0; i < le32_to_cpu(pdacl->num_aces); i++) { - if (offsetof(struct smb_ace, access_req) > aces_size) + if (offsetof(struct smb_ace, sid) + + aces_size < CIFS_SID_BASE_SIZE) break; ace_size = le16_to_cpu(ace->size); - if (ace_size > aces_size) + if (ace_size > aces_size || + ace_size < offsetof(struct smb_ace, sid) + + CIFS_SID_BASE_SIZE) break; aces_size -= ace_size; + if (ace->sid.num_subauth > SID_MAX_SUB_AUTHORITIES) + break; + if (!compare_sids(&sid, &ace->sid) || !compare_sids(&sid_unix_NFS_mode, &ace->sid)) { found = 1;