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 4A8A5215075; Thu, 20 Aug 2026 17:53:51 +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=1787248432; cv=none; b=t1g5qsJgAQHsnivTE2CRMAIKAgDwLI55nCOfJyefeNfS8tu4kf14v8hK0Aw8eYQIAkb+0ZSgPeCEuD68tNNcMVIQueLE/OL6Vd0JhAvZfzso52U04Ss0axbkIYJ2jN0wAn19THJ0jvKUvvBBhQ0yAGLpK0toRxYAwn0fHDJqqr4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787248432; c=relaxed/simple; bh=qcp6/NVzY/e4amubpOxPGZLuWqQ/wIS8vwPHj6/sdos=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=hzJ1RmYRjYrDrliyKzOV/7hHQXeiI72n4BAB0jg1VcYWCv4zxG0ggrz2VMWJAW0KvoVb1CAoHHELuE/9kJyqMBL9IyDS1f4S00ZHWaL4wSpovuxT9mJpBQXK1ECDJ5nDGMsChWtixJ8nDq0YrZbGnCs7aY4iR+0GR4K4XnHC6sc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FGQvFoV4; 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="FGQvFoV4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A63031F000E9; Thu, 20 Aug 2026 17:53:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787248431; bh=MNgA1b3FpVwBsa5kvetA2oRuehgXIzWXjb1Jq1YZyV4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FGQvFoV4aXArGjp4HH9Jq44bsg0RyMLOSW+vCHucGefd3s6dGFHDTvzYZ/tKPIy9p Wd2ypHMfwRHfwIldqfiO/4ozUbYHdO+chvm06Em842I74A11eMIOOo0lHkNS+y8o0z iHrWTcG6yicElRdjLxiIizt0LmI1DLMGFYAwTdiU= 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 6.1 224/303] ksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL Date: Thu, 20 Aug 2026 16:56:00 +0200 Message-ID: <20260820145300.141323592@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260820145253.200766705@linuxfoundation.org> References: <20260820145253.200766705@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 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wentao Guan [ Upstream commit bbf0a8e931204ecdab494a88d43b0a24a04285c5 ] 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 Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/smbacl.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/fs/smb/server/smbacl.c +++ b/fs/smb/server/smbacl.c @@ -644,6 +644,7 @@ static void set_posix_acl_entries_dacl(s 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; } @@ -658,6 +659,7 @@ static void set_posix_acl_entries_dacl(s 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; } @@ -703,6 +705,7 @@ posix_default_acl: 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; } @@ -745,8 +748,10 @@ static void set_ntacl_dacl(struct user_n 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: