From mboxrd@z Thu Jan 1 00:00:00 1970 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 667FB3A6F01 for ; Tue, 12 May 2026 14:04:53 +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=1778594693; cv=none; b=GegeYFaTxszs7PQZBcSRVPtv0exeNKJnA9loVZ961bzYRfieU7Yo8nStHSn/lQsokXiXan1VTulCpzzNdqzhV/lk8hC/TJ4AYvxDueMz1XOycxrRYen7ju7Pi3PNjDk/jGqpeQ/J1vMiHdZMx+p3+cWRXSuQui7kdOCSQwVZ6x8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778594693; c=relaxed/simple; bh=y6+rEPpJnsZOHaw9Lx9JYiMACg3aCxIQoAUiOasIeXI=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=mE0xe6z7UTzMWHsbs/awPSl88880BuI3EjMCYhhBuclTuiq2pkacmIbaB8KCwbMJ6z2mMnmJDu6q5yfbQEBd1Fg8uJ4QnV4+t9jUFsw9gpfn9jSWQx7abomYaXE/hJNAz5r8OpIlksaHMtMNjTpxTYjnCV9rPlFKhlrR9MwbhcI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=JPrmZgwr; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="JPrmZgwr" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A5CEDC2BCB0; Tue, 12 May 2026 14:04:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778594693; bh=y6+rEPpJnsZOHaw9Lx9JYiMACg3aCxIQoAUiOasIeXI=; h=Subject:To:Cc:From:Date:From; b=JPrmZgwrMTfOkGs0LU+ptwWlLdWSyHPKeMMM5APM3rWGGCarO7SdoDPiPatMHADPA u1ZSrMNdOhBDNOW/+PMVila3gyXwPfp6qPs0QjHTyf5umRWgK4NU1S/jMnQNGCAXdm NlLlDEvQQABomA2V5U/8tpanJ8lL2HUJgn39iDkQ= Subject: FAILED: patch "[PATCH] smb: client: validate dacloffset before building DACL" failed to apply to 5.15-stable tree To: michael.bommarito@gmail.com,stfrench@microsoft.com Cc: From: Date: Tue, 12 May 2026 16:04:49 +0200 Message-ID: <2026051249-smartness-undercoat-cf5c@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x f98b48151cc502ada59d9778f0112d21f2586ca3 # git commit -s git send-email --to '' --in-reply-to '2026051249-smartness-undercoat-cf5c@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From f98b48151cc502ada59d9778f0112d21f2586ca3 Mon Sep 17 00:00:00 2001 From: Michael Bommarito Date: Mon, 20 Apr 2026 10:47:47 -0400 Subject: [PATCH] smb: client: validate dacloffset before building DACL pointers parse_sec_desc(), build_sec_desc(), and the chown path in id_mode_to_cifs_acl() all add the server-supplied dacloffset to pntsd before proving a DACL header fits inside the returned security descriptor. On 32-bit builds a malicious server can return dacloffset near U32_MAX, wrap the derived DACL pointer below end_of_acl, and then slip past the later pointer-based bounds checks. build_sec_desc() and id_mode_to_cifs_acl() can then dereference DACL fields from the wrapped pointer in the chmod/chown rewrite paths. Validate dacloffset numerically before building any DACL pointer and reuse the same helper at the three DACL entry points. Fixes: bc3e9dd9d104 ("cifs: Change SIDs in ACEs while transferring file ownership.") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Michael Bommarito Signed-off-by: Steve French diff --git a/fs/smb/client/cifsacl.c b/fs/smb/client/cifsacl.c index a2750f1e3d90..786dbbc43c5b 100644 --- a/fs/smb/client/cifsacl.c +++ b/fs/smb/client/cifsacl.c @@ -1264,6 +1264,17 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl) return 0; } +static bool dacl_offset_valid(unsigned int acl_len, __u32 dacloffset) +{ + if (acl_len < sizeof(struct smb_acl)) + return false; + + if (dacloffset < sizeof(struct smb_ntsd)) + return false; + + return dacloffset <= acl_len - sizeof(struct smb_acl); +} + /* Convert CIFS ACL to POSIX form */ static int parse_sec_desc(struct cifs_sb_info *cifs_sb, @@ -1284,7 +1295,6 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb, group_sid_ptr = (struct smb_sid *)((char *)pntsd + le32_to_cpu(pntsd->gsidoffset)); dacloffset = le32_to_cpu(pntsd->dacloffset); - dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset); cifs_dbg(NOISY, "revision %d type 0x%x ooffset 0x%x goffset 0x%x sacloffset 0x%x dacloffset 0x%x\n", pntsd->revision, pntsd->type, le32_to_cpu(pntsd->osidoffset), le32_to_cpu(pntsd->gsidoffset), @@ -1315,11 +1325,18 @@ static int parse_sec_desc(struct cifs_sb_info *cifs_sb, return rc; } - if (dacloffset) + if (dacloffset) { + if (!dacl_offset_valid(acl_len, dacloffset)) { + cifs_dbg(VFS, "Server returned illegal DACL offset\n"); + return -EINVAL; + } + + dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset); parse_dacl(dacl_ptr, end_of_acl, owner_sid_ptr, group_sid_ptr, fattr, get_mode_from_special_sid); - else + } else { cifs_dbg(FYI, "no ACL\n"); /* BB grant all or default perms? */ + } return rc; } @@ -1342,6 +1359,11 @@ static int build_sec_desc(struct smb_ntsd *pntsd, struct smb_ntsd *pnntsd, dacloffset = le32_to_cpu(pntsd->dacloffset); if (dacloffset) { + if (!dacl_offset_valid(secdesclen, dacloffset)) { + cifs_dbg(VFS, "Server returned illegal DACL offset\n"); + return -EINVAL; + } + dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset); rc = validate_dacl(dacl_ptr, end_of_acl); if (rc) @@ -1710,6 +1732,12 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode, nsecdesclen = sizeof(struct smb_ntsd) + (sizeof(struct smb_sid) * 2); dacloffset = le32_to_cpu(pntsd->dacloffset); if (dacloffset) { + if (!dacl_offset_valid(secdesclen, dacloffset)) { + cifs_dbg(VFS, "Server returned illegal DACL offset\n"); + rc = -EINVAL; + goto id_mode_to_cifs_acl_exit; + } + dacl_ptr = (struct smb_acl *)((char *)pntsd + dacloffset); rc = validate_dacl(dacl_ptr, (char *)pntsd + secdesclen); if (rc) { @@ -1752,6 +1780,7 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode, rc = ops->set_acl(pnntsd, nsecdesclen, inode, path, aclflag); cifs_dbg(NOISY, "set_cifs_acl rc: %d\n", rc); } +id_mode_to_cifs_acl_exit: cifs_put_tlink(tlink); kfree(pnntsd);