[patch 4/7] vfs: O_* bit numbers uniqueness check

[patch 4/7] vfs: O_* bit numbers uniqueness check

[akpm]

From: Wu Fengguang <fengguang.wu@intel.com>

The O_* bit numbers are defined in 20+ arch/*, and can silently overlap. 
Add a compile time check to ensure the uniqueness as suggested by David
Miller.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: David Miller <davem@davemloft.net>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Eric Paris <eparis@redhat.com>
Cc: Roland Dreier <rdreier@cisco.com>
Cc: Jamie Lokier <jamie@shareable.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/fcntl.c                  |   15 +++++++++++++--
 include/asm-generic/fcntl.h |    4 ++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff -puN fs/fcntl.c~vfs-o_-bit-numbers-uniqueness-check fs/fcntl.c
--- a/fs/fcntl.c~vfs-o_-bit-numbers-uniqueness-check
+++ a/fs/fcntl.c
@@ -757,11 +757,22 @@ void kill_fasync(struct fasync_struct **
 }
 EXPORT_SYMBOL(kill_fasync);
 
-static int __init fasync_init(void)
+static int __init fcntl_init(void)
 {
+	/* please add new bits here to ensure allocation uniqueness */
+	BUILD_BUG_ON(19 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
+		O_RDONLY	| O_WRONLY	| O_RDWR	|
+		O_CREAT		| O_EXCL	| O_NOCTTY	|
+		O_TRUNC		| O_APPEND	| O_NONBLOCK	|
+		__O_SYNC	| O_DSYNC	| FASYNC	|
+		O_DIRECT	| O_LARGEFILE	| O_DIRECTORY	|
+		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC	|
+		FMODE_EXEC
+		));
+
 	fasync_cache = kmem_cache_create("fasync_cache",
 		sizeof(struct fasync_struct), 0, SLAB_PANIC, NULL);
 	return 0;
 }
 
-module_init(fasync_init)
+module_init(fcntl_init)
diff -puN include/asm-generic/fcntl.h~vfs-o_-bit-numbers-uniqueness-check include/asm-generic/fcntl.h
--- a/include/asm-generic/fcntl.h~vfs-o_-bit-numbers-uniqueness-check
+++ a/include/asm-generic/fcntl.h
@@ -11,6 +11,10 @@
  * -Eric Paris
  */
 
+/*
+ * When introducing new O_* bits, please check its uniqueness in fcntl_init().
+ */
+
 #define O_ACCMODE	00000003
 #define O_RDONLY	00000000
 #define O_WRONLY	00000001
_