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 4E2453890F3 for ; Fri, 24 Apr 2026 09:41:29 +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=1777023689; cv=none; b=tOwIfUq1f3f+yYgRxcKaYlCv7wfu1fW3+FCEnleEpkoEPhnlSVZuKVF/qs89c+OEA+/rGrPtqW3SOzLDDYWHalN8tRSnfmEE1xxpIj3yXeGSEYoHwlmXh4qlhFTkpAOsKD4dAjAceONuvv9qoA6zLBEn9jQDObskeEn7QwlAw68= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777023689; c=relaxed/simple; bh=xtAkP6GH6U9AIXuUTsHcDAjD5wuzECb5Q/FOhv/sjgY=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=hPH9j6mvk3IymTbHIAdjNPUZvIdpoCKMYcRajp41zoqvVkOIrNjNfaUVQgfs+d/XA6bnhEaPtD6bOR/QrK7QMbNyyvYuZvUhWNEz6I4FAocvMzMNwiAk8RaNGRvVPqMO209oOF34KvEYnpHted9ymJc6CSh1Y4XX5O7JkzKrfw4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=XlMm9uUT; 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="XlMm9uUT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CC9BEC19425; Fri, 24 Apr 2026 09:41:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1777023689; bh=xtAkP6GH6U9AIXuUTsHcDAjD5wuzECb5Q/FOhv/sjgY=; h=Subject:To:Cc:From:Date:From; b=XlMm9uUTEJcQD9CEU7JOZPJnq2qiWI6M+YK0tYHT6jv7uZcUdg3Lq+jAAJe7jrTxt IismpMi3X2uYbSN/GsoppsA8HWjGsDxWAMOdUaa9Dah4+DXKPZyv4W8hbonuLQUdw9 TwXmD32Xrwz+IPp/cKHYFBpYuKE1oVvfwYWiiiI4= Subject: FAILED: patch "[PATCH] ksmbd: require minimum ACE size in smb_check_perm_dacl()" failed to apply to 6.6-stable tree To: michael.bommarito@gmail.com,linkinjeon@kernel.org,stfrench@microsoft.com Cc: From: Date: Fri, 24 Apr 2026 11:41:26 +0200 Message-ID: <2026042426-growing-dime-ce6e@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 6.6-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-6.6.y git checkout FETCH_HEAD git cherry-pick -x d07b26f39246a82399661936dd0c853983cfade7 # git commit -s git send-email --to '' --in-reply-to '2026042426-growing-dime-ce6e@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d07b26f39246a82399661936dd0c853983cfade7 Mon Sep 17 00:00:00 2001 From: Michael Bommarito Date: Tue, 14 Apr 2026 15:15:33 -0400 Subject: [PATCH] ksmbd: require minimum ACE size in smb_check_perm_dacl() 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 diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c index 061a305bf9c8..bba26a0355bb 100644 --- a/fs/smb/server/smbacl.c +++ b/fs/smb/server/smbacl.c @@ -1342,10 +1342,13 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path, ace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl)); aces_size = acl_size - sizeof(struct smb_acl); for (i = 0; i < le16_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); @@ -1360,13 +1363,19 @@ int smb_check_perm_dacl(struct ksmbd_conn *conn, const struct path *path, ace = (struct smb_ace *)((char *)pdacl + sizeof(struct smb_acl)); aces_size = acl_size - sizeof(struct smb_acl); for (i = 0; i < le16_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;