From 356c289c25884fd6b060f0636c48aafeeb974ab6 Mon Sep 17 00:00:00 2001
From: ngie <ngie@FreeBSD.org>
Date: Tue, 16 Sep 2014 00:56:47 +0000
Subject: [PATCH] Validate the mode argument in access, eaccess, and faccessat
 for optional POSIX compliance and to improve compatibility with Linux and
 NetBSD

The issue was identified with lib/libc/sys/t_access:access_inval from
NetBSD

Update the manpage accordingly

PR: 181155
Reviewed by: jilles (code), jmmv (code), wblock (manpage), wollman (code)
MFC after: 4 weeks
Phabric: D678 (code), D786 (manpage)
Sponsored by: EMC / Isilon Storage Division
---
 lib/libc/sys/access.2   | 10 +++++++++-
 sys/kern/vfs_syscalls.c |  3 +++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/lib/libc/sys/access.2 b/lib/libc/sys/access.2
index 65b8fb6bfbb1..edc6194756cc 100644
--- a/lib/libc/sys/access.2
+++ b/lib/libc/sys/access.2
@@ -133,8 +133,16 @@ and
 .Sh RETURN VALUES
 .Rv -std
 .Sh ERRORS
-Access to the file is denied if:
+.Fn access ,
+.Fn eaccess ,
+or
+.Fn faccessat 
+will fail if:
 .Bl -tag -width Er
+.It Bq Er EINVAL
+The value of the
+.Fa mode
+argument is invalid.
 .It Bq Er ENOTDIR
 A component of the path prefix is not a directory.
 .It Bq Er ENAMETOOLONG
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 1406e0f8bc5f..b3b7ed5defd9 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -2055,6 +2055,9 @@ kern_accessat(struct thread *td, int fd, char *path, enum uio_seg pathseg,
 	cap_rights_t rights;
 	int error;
 
+	if (amode != F_OK && (amode & ~(R_OK | W_OK | X_OK)) != 0)
+		return (EINVAL);
+
 	/*
 	 * Create and modify a temporary credential instead of one that
 	 * is potentially shared.