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 7A4143B6366; Thu, 30 Jul 2026 14:54:16 +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=1785423257; cv=none; b=uEArjMNOCZIuV23H0jsPc/tEK/lmcKEFgjTWyzo2ztb6iIbV8dEl6+O3UqJxbykI/K3xrgYyBrFk1KpRLmeYhnJlyRanPCsBe0nBQ/nGpMwUtSvKyK5r7axESNxFG7Bw7EBf2X8GD/DOCNV57Uppru489eFoCd26Hz/EBEdoIAI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785423257; c=relaxed/simple; bh=umx89c4Y7VySoihNSDK79EzAsJcNX4vrxyBzngJ/dj4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=pD99jFcFZZQQBrFAhoxaQe5jwRtDiFuWTDtXEZ10YrkSZAqjHoRq30jg8zgF3K1fCLP4CvIjQ2xSKzzivFbYWWZ3zBE7m0UFpzTwZun5G52kylxw6N8V3h+Oc6muMKCnnBpnyqEbcRurthxxG7fTxCNKxQKXrGSJKrn0zm2vwXQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CooGm307; 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="CooGm307" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D11D71F000E9; Thu, 30 Jul 2026 14:54:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785423256; bh=0DJAfDwyC1/Kmw1kM9Q1PKpDBTJr60YeFyku2bcTvh0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=CooGm307gcuxaRGKaW7in9vCz7v8ewc1zRwfhsv67ODA5A6OEycinPajMZq01Kd9L FZqW+oY866BPtxTYMQzfIwAz2BiT6V5Fi8rlAWYwrxtgro/Ywdw45OxyZG0dWgiLiu XhivyoWX5LR9xkRThKVDsxAsC+9rEVL9t2941VUM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Wentao Guan , Namjae Jeon , Steve French , Sasha Levin Subject: [PATCH 7.1 721/744] ksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL Date: Thu, 30 Jul 2026 16:16:34 +0200 Message-ID: <20260730141459.606285796@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141444.267951807@linuxfoundation.org> References: <20260730141444.267951807@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 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wentao Guan commit bbf0a8e931204ecdab494a88d43b0a24a04285c5 upstream. check_add_overflow() unconditionally writes the truncated sum into *d even on overflow, per its contract in include/linux/overflow.h. The four check_add_overflow() guards in set_posix_acl_entries_dacl() and set_ntacl_dacl() break out of the ACE-building loops on overflow, but the truncated *size is then consumed downstream at the end of set_ntacl_dacl(): pndacl->size = cpu_to_le16(le16_to_cpu(pndacl->size) + size); This produces an on-wire NT ACL whose pndacl->size under-reports the bytes actually written by the preceding fill_ace_for_sid()/memcpy() calls, yielding a malformed ACL that can trigger out-of-bounds reads when re-parsed by clients or ksmbd itself. Restore *size to its pre-addition value on each overflow branch (via `*size -= ace_sz` / `size -= nt_ace_size`) so that after the break, *size once again holds the cumulative size of the successfully-written ACEs. The committed ACL is then truncated-but-self-consistent rather than malformed. The ksmbd DACL builders are the only check_add_overflow() sites found where an overflow path breaks out of a loop and the destination value is consumed afterward. The other nearby break-style cases either return -EINVAL on overflow (transport_ipc.c) or break without consuming the overflowed destination value afterward (buildid.c). Fixes: 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow") Assisted-by: atomcode:glm-5.2 Assisted-by: Codex:gpt-5.5 Cc: stable@vger.kernel.org Signed-off-by: Wentao Guan Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/smb/server/smbacl.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c index 9c59c8f73b6675..5621c50a805716 100644 --- a/fs/smb/server/smbacl.c +++ b/fs/smb/server/smbacl.c @@ -649,6 +649,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap, ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, flags, pace->e_perm, 0777); if (check_add_overflow(*size, ace_sz, size)) { + *size -= ace_sz; kfree(sid); break; } @@ -663,6 +664,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap, ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, 0x03, pace->e_perm, 0777); if (check_add_overflow(*size, ace_sz, size)) { + *size -= ace_sz; kfree(sid); break; } @@ -708,6 +710,7 @@ static void set_posix_acl_entries_dacl(struct mnt_idmap *idmap, ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, 0x0b, pace->e_perm, 0777); if (check_add_overflow(*size, ace_sz, size)) { + *size -= ace_sz; kfree(sid); break; } @@ -750,8 +753,10 @@ static void set_ntacl_dacl(struct mnt_idmap *idmap, goto next_ace; memcpy((char *)pndace + size, ntace, nt_ace_size); - if (check_add_overflow(size, nt_ace_size, &size)) + if (check_add_overflow(size, nt_ace_size, &size)) { + size -= nt_ace_size; break; + } num_aces++; next_ace: -- 2.53.0