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Subject[PATCH 3/6] vfs: O_* bit numbers uniqueness check
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.
v4: use the nice hweight_long() (suggested by Jamie)
split O_SYNC to (__O_SYNC | O_DSYNC) (suggested by Andreas)
take away the FMODE_* and O_RANDOM bits
v3: change to BUILD_BUG_ON() (suggested by Roland)
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: Wu Fengguang <fengguang.wu@intel.com>
---
fs/fcntl.c | 14 ++++++++++++--
include/asm-generic/fcntl.h | 2 ++
2 files changed, 14 insertions(+), 2 deletions(-)
--- linux.orig/fs/fcntl.c 2010-01-09 11:02:57.000000000 +0800
+++ linux/fs/fcntl.c 2010-01-09 21:36:16.000000000 +0800
@@ -709,11 +709,21 @@ 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(17 != hweight_long(
+ 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
+ ));
+
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)
--- linux.orig/include/asm-generic/fcntl.h 2010-01-09 11:02:57.000000000 +0800
+++ linux/include/asm-generic/fcntl.h 2010-01-09 12:23:17.000000000 +0800
@@ -4,6 +4,8 @@
#include <linux/types.h>

/*
+ * When introducing new O_* bits, please check its uniqueness in fcntl_init().
+ *
* FMODE_EXEC is 0x20
* FMODE_NONOTIFY is 0x1000000
* These cannot be used by userspace O_* until internal and external open



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