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 56DBB582B98 for ; Thu, 17 Sep 2026 14:08:53 +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=1789654138; cv=none; b=DGM8FssBaR7EYSkRUT+q2HkS0W9OKGpTgsU0ujnC0dJshxD8oMaps/9iHnht0UX3xA2bbDTdjxXk6NOGvExgf1wwijgcPem7jW8RzDyjPKa9B0YKr2gkRkkqCLymp8mpxP9te7GW5KsNUM6/Xp18J26/CLOPMK4JyBcRoMIqNXY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789654138; c=relaxed/simple; bh=3iKNf6gqGztug3DoVKS0TRRVnL6k0EuyVwqQeY79NQM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=WYN3Ecvv0tPxoFUYSKcGeturFCddGe2B5UoQ/B9Bp2HU4KJp7AYzWn/EIUt4Hjk8ZckGpde6srSPyhDEhRuw4gczoSLpgeGbep/PAoGI1nKZ6qTuuc5Qn35PVB/wGumi5JgAhblJ9i1hUdJAHQNKTSO3hF79B2IL/ivAOPV4mXc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jmYphoe5; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jmYphoe5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 568601F000FF; Thu, 17 Sep 2026 14:08:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789654130; bh=aSxQr5T7TYtIkCGpHdqb5W7ws+71Y4gUXDG4gy1T4C0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=jmYphoe5hlr9t1R6cxglI17+MteihorJmwblKc1lAdypQXYYHR2hDDb2sYLrlP8YK A0Gh36QDprB9gp+1AJ6lOmzKRQ1h+riwxlf4f7vFIJmFLpbTI/WJ+cHuFm2+y77jYZ tQwQHHR+xUdI6v9kSAbMRDs6QJEdBKM7piMwqZd9umq1UxhdTexKlznXL0YbI7LLTY kwAte+wLiCbNWN9BbwJxqtIFrYSiBSXLT/I4HPdd1K77xdQTehfknBRRd9CBe1ibpX oCgCiQlJkYARmftzji8PcVqHxKT0XDFzzu3HwJgZbt0M/uDwsS0cVscY5CHG9zhhEV BUk7jiWOnbidA== From: Sasha Levin To: stable@vger.kernel.org Cc: Bjoern Doebel , Namjae Jeon , Paulo Alcantara , Sasha Levin Subject: [PATCH 5.15.y] smb: client: fix heap overflow in DACL owner/group rewrite Date: Thu, 17 Sep 2026 10:08:48 -0400 Message-ID: <20260917140848.514192-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026091607-trouble-defuse-0631@gregkh> References: <2026091607-trouble-defuse-0631@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=UTF-8 Content-Transfer-Encoding: 8bit From: Bjoern Doebel [ Upstream commit 0ee150794c75bcd0be0e24ff3394f433cbae18cc ] When id_mode_to_cifs_acl rewrites an existing DACL, it allocates a buffer sized according to the on-disk DACL length reported by dacl_ptr->size. However, replace_sids_and_copy_aces may rewrite each ACE with a new owner/group SID obtained from the cifs.idmap upcall. Those SIDs can have up to SID_MAX_SUB_AUTHORITIES (15) sub-authorities, making each ACE up to 76 bytes (sizeof(struct smb_ace)). If the original DACL contains short SIDs (e.g., 1 sub-authority) while the replacement SIDs are long, the rewritten ACEs overflow the allocation. Fix this by always budgeting for worst-case SID expansion: allocate sizeof(struct smb_acl) plus num_aces * sizeof(struct smb_ace), which covers the smb_acl header and room for every ACE at maximum SID size. This replaces the previous split logic that used dacl_ptr->size for cifsacl mounts but num_aces * sizeof(struct smb_ace) for mode_from_sid mounts: both paths can trigger the same rewrite and need the same headroom. KASAN reports this as: BUG: KASAN: slab-out-of-bounds in build_sec_desc+0x1e8a/0x2680 [cifs] Write of size 4 at addr ffff8881a5e25374 by task chown/5298 ... The buggy address is located 0 bytes to the right of allocated 884-byte region [ffff8881a5e25000, ffff8881a5e25374) Cc: stable@vger.kernel.org Fixes: bc3e9dd9d104 ("cifs: Change SIDs in ACEs while transferring file ownership.") Assisted-by: Kiro:claude-opus-4.6 Signed-off-by: Bjoern Doebel Reviewed-by: Namjae Jeon Fixes: 5c3564852c58 ("cifs: Minimize the number of cifs_acl memory allocations") Signed-off-by: Paulo Alcantara [ changed smb_acl/smb_ace to cifs_acl/cifs_ace and le16_to_cpu() to le32_to_cpu() for the branch’s 32-bit num_aces field. ] Signed-off-by: Sasha Levin --- fs/cifs/cifsacl.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c index 1b52e0c88877a..c921d6e2dd51b 100644 --- a/fs/cifs/cifsacl.c +++ b/fs/cifs/cifsacl.c @@ -1729,11 +1729,13 @@ id_mode_to_cifs_acl(struct inode *inode, const char *path, __u64 *pnmode, cifs_put_tlink(tlink); return rc; } - if (mode_from_sid) - nsecdesclen += - le32_to_cpu(dacl_ptr->num_aces) * sizeof(struct cifs_ace); - else /* cifsacl */ - nsecdesclen += le16_to_cpu(dacl_ptr->size); + /* + * Worst case: every ACE is rewritten with a new SID of + * SID_MAX_SUB_AUTHORITIES sub-auths -> sizeof(cifs_ace) each, + * plus the cifs_acl header replace_sids_and_copy_aces() emits. + */ + nsecdesclen += sizeof(struct cifs_acl) + + le32_to_cpu(dacl_ptr->num_aces) * sizeof(struct cifs_ace); } } -- 2.53.0