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 CD83E358373; Thu, 30 Jul 2026 15:48:58 +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=1785426539; cv=none; b=a3Koi957ER9BTLvGPAPpDH9qg1A2CilJi3sGE0P18XtCDaeAdPOg4L613adh8sBjrH9P+l5921390lb+sO1lqGTe9Qm61KLIxIXkqpHogqV1TaNq+9W7TIsp2/KGd3R5SNg3Il/s2962ctCQa9qt0R1/I3vru5m87ZnnPU7Psp4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785426539; c=relaxed/simple; bh=InovPMmftiSt/osFCrfPhcT0xk2G9LnUpmMmXUeX0cE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hrYSZW7/CkosBhnUpghlxRDQIm/Z38RVaEJSGvFsn8FolKXHMkkzfaBE7B3aC6Wry0dwiY6QmmMzqHq2isozt0bodc+Av0VRlz9M4DihD+P3d75fCOBJOkbROIt4GPqeqjS5pTodTEEskLTVwQPs84OX0oZ79D3xgMzzfl/+QdI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=WYBhXA8T; 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="WYBhXA8T" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B99B1F000E9; Thu, 30 Jul 2026 15:48:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785426538; bh=4NXEbxf+Ep0MijOESLkpIKSAYjvO/GYet5SjsWoG/zU=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WYBhXA8TFnBIAL/AobP/HkZTImIG7ap7eBjtnVy6x8ekvXvz83OGQfpug0vxb+Oh6 vDKk7olC3qBm7s2V7VFPyeb0JBhnzxaslWtdFq9yFrgEqCIeUxqzKeioofvK3YAgdN ScvDXv4/8i2HYXL8lY+Qu2cMyx6uJLPe07YEogRQ= 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 6.12 454/602] ksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL Date: Thu, 30 Jul 2026 16:14:06 +0200 Message-ID: <20260730141445.498527359@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141435.976815864@linuxfoundation.org> References: <20260730141435.976815864@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 6.12-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 173469d112f101..ca0e4aab6dd87f 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