[patch 4/6] vfs: O_* bit numbers uniqueness check

[patch 4/6] 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                  |   14 ++++++++++++--
 include/asm-generic/fcntl.h |    2 ++
 2 files changed, 14 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
@@ -739,11 +739,21 @@ 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 != 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
+		));
+
 	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
@@ -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
_

Re: [patch 4/6] vfs: O_* bit numbers uniqueness check

[Eric Paris]

On Thu, 2010-03-11 at 14:11 -0800, akpm@linux-foundation.org wrote:
> 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.

Until the FMODE_ and O_ bits do not overload I think we need to check
FMODE_EXEC and FMODE_NONOTIFY (if you have that one) inside fcntl_init()
as well.  I guess I'll send a patch to someone ?Al? to add FMODE_EXEC to
the list....

-Eric

> 
> 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                  |   14 ++++++++++++--
>  include/asm-generic/fcntl.h |    2 ++
>  2 files changed, 14 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
> @@ -739,11 +739,21 @@ 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 != 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
> +		));
> +
>  	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
> @@ -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
> _

Re: [patch 4/6] vfs: O_* bit numbers uniqueness check

[Andreas Dilger]

On 2010-03-11, at 15:11, akpm@linux-foundation.org wrote:
> +static int __init fcntl_init(void)
> {
> +	/* please add new bits here to ensure allocation uniqueness */
> +	BUILD_BUG_ON(17 != 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
> +		));


It's non-obvious why there are 18 flags listed here, but the hweight  
is only 17?  Presumably this is because O_RDONLY has value 0, but that  
should at least be
listed in a comment, or the test could be written more explicitly, like:

          BUILD_BUG_ON(18 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
                       ...

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

[PATCH] vfs: O_* bit numbers uniqueness check fix

[Wu Fengguang]

Follow the comment by Eric:

	Until the FMODE_ and O_ bits do not overload I think we need to check
	FMODE_EXEC and FMODE_NONOTIFY (if you have that one) inside fcntl_init()
	as well.  I guess I'll send a patch to someone ?Al? to add FMODE_EXEC to
	the list....

CC: Eric Paris <eparis@redhat.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 fs/fcntl.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- linux-mm.orig/fs/fcntl.c	2010-03-12 21:27:12.000000000 +0800
+++ linux-mm/fs/fcntl.c	2010-03-12 21:38:51.000000000 +0800
@@ -748,7 +748,8 @@ static int __init fcntl_init(void)
 		O_TRUNC		| O_APPEND	| O_NONBLOCK	|
 		__O_SYNC	| O_DSYNC	| FASYNC	|
 		O_DIRECT	| O_LARGEFILE	| O_DIRECTORY	|
-		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC
+		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC	|
+		FMODE_EXEC
 		));
 
 	fasync_cache = kmem_cache_create("fasync_cache",

[PATCH] vfs: O_* bit numbers uniqueness check fix 2

[Wu Fengguang]

Follow the comment by Andreas:

	It's non-obvious why there are 18 flags listed here, but the hweight
	is only 17?  Presumably this is because O_RDONLY has value 0, but that
	should at least be
	listed in a comment, or the test could be written more explicitly, like:

		  BUILD_BUG_ON(18 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(


CC: Andreas Dilger <adilger@sun.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 fs/fcntl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-mm.orig/fs/fcntl.c	2010-03-12 21:39:01.000000000 +0800
+++ linux-mm/fs/fcntl.c	2010-03-12 21:38:42.000000000 +0800
@@ -742,7 +742,7 @@ EXPORT_SYMBOL(kill_fasync);
 static int __init fcntl_init(void)
 {
 	/* please add new bits here to ensure allocation uniqueness */
-	BUILD_BUG_ON(17 != HWEIGHT32(
+	BUILD_BUG_ON(18 - 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	|

Re: [PATCH] vfs: O_* bit numbers uniqueness check fix

[Eric Paris]

On Fri, 2010-03-12 at 21:41 +0800, Wu Fengguang wrote:
> Follow the comment by Eric:
> 
> 	Until the FMODE_ and O_ bits do not overload I think we need to check
> 	FMODE_EXEC and FMODE_NONOTIFY (if you have that one) inside fcntl_init()
> 	as well.  I guess I'll send a patch to someone ?Al? to add FMODE_EXEC to
> 	the list....
> 
> CC: Eric Paris <eparis@redhat.com>
> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> ---
>  fs/fcntl.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> --- linux-mm.orig/fs/fcntl.c	2010-03-12 21:27:12.000000000 +0800
> +++ linux-mm/fs/fcntl.c	2010-03-12 21:38:51.000000000 +0800
> @@ -748,7 +748,8 @@ static int __init fcntl_init(void)
>  		O_TRUNC		| O_APPEND	| O_NONBLOCK	|
>  		__O_SYNC	| O_DSYNC	| FASYNC	|
>  		O_DIRECT	| O_LARGEFILE	| O_DIRECTORY	|
> -		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC
> +		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC	|
> +		FMODE_EXEC
>  		));

I think we need to update the hweight as well, otherwise I sure hope
this would panic....

-Eric

Re: [PATCH] vfs: O_* bit numbers uniqueness check fix

[Wu Fengguang]

On Fri, Mar 12, 2010 at 11:01:27PM +0800, Eric Paris wrote:
> On Fri, 2010-03-12 at 21:41 +0800, Wu Fengguang wrote:
> > Follow the comment by Eric:
> > 
> > 	Until the FMODE_ and O_ bits do not overload I think we need to check
> > 	FMODE_EXEC and FMODE_NONOTIFY (if you have that one) inside fcntl_init()
> > 	as well.  I guess I'll send a patch to someone ?Al? to add FMODE_EXEC to
> > 	the list....
> > 
> > CC: Eric Paris <eparis@redhat.com>
> > Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
> > ---
> >  fs/fcntl.c |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > --- linux-mm.orig/fs/fcntl.c	2010-03-12 21:27:12.000000000 +0800
> > +++ linux-mm/fs/fcntl.c	2010-03-12 21:38:51.000000000 +0800
> > @@ -748,7 +748,8 @@ static int __init fcntl_init(void)
> >  		O_TRUNC		| O_APPEND	| O_NONBLOCK	|
> >  		__O_SYNC	| O_DSYNC	| FASYNC	|
> >  		O_DIRECT	| O_LARGEFILE	| O_DIRECTORY	|
> > -		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC
> > +		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC	|
> > +		FMODE_EXEC
> >  		));
> 
> I think we need to update the hweight as well, otherwise I sure hope
> this would panic....

Ah faint.. Here is the fixed one.

Thanks,
Fengguang
---
Subject: vfs: O_* bit numbers uniqueness check fix
From: Wu Fengguang <fengguang.wu@intel.com>
Date: Fri Mar 12 21:38:54 CST 2010

Follow the comment by Eric:

	Until the FMODE_ and O_ bits do not overload I think we need to check
	FMODE_EXEC and FMODE_NONOTIFY (if you have that one) inside fcntl_init()
	as well.  I guess I'll send a patch to someone ?Al? to add FMODE_EXEC to
	the list....

CC: Eric Paris <eparis@redhat.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 fs/fcntl.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- linux-mm.orig/fs/fcntl.c	2010-03-12 21:27:12.000000000 +0800
+++ linux-mm/fs/fcntl.c	2010-03-12 23:11:46.000000000 +0800
@@ -742,13 +742,14 @@ EXPORT_SYMBOL(kill_fasync);
 static int __init fcntl_init(void)
 {
 	/* please add new bits here to ensure allocation uniqueness */
-	BUILD_BUG_ON(17 != HWEIGHT32(
+	BUILD_BUG_ON(18 != 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
+		O_NOFOLLOW	| O_NOATIME	| O_CLOEXEC	|
+		FMODE_EXEC
 		));
 
 	fasync_cache = kmem_cache_create("fasync_cache",

Re: [PATCH] vfs: O_* bit numbers uniqueness check fix

[Wu Fengguang]

> > I think we need to update the hweight as well, otherwise I sure hope
> > this would panic....
> 
> Ah faint.. Here is the fixed one.

And the second one.

---
Subject: vfs: O_* bit numbers uniqueness check fix 2
From: Wu Fengguang <fengguang.wu@intel.com>
Date: Fri Mar 12 21:39:10 CST 2010

Follow the comment by Andreas:

	It's non-obvious why there are 18 flags listed here, but the hweight
	is only 17?  Presumably this is because O_RDONLY has value 0, but that
	should at least be
	listed in a comment, or the test could be written more explicitly, like:

		  BUILD_BUG_ON(18 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(


CC: Andreas Dilger <adilger@sun.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
 fs/fcntl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-mm.orig/fs/fcntl.c	2010-03-12 23:11:46.000000000 +0800
+++ linux-mm/fs/fcntl.c	2010-03-12 23:12:05.000000000 +0800
@@ -742,7 +742,7 @@ EXPORT_SYMBOL(kill_fasync);
 static int __init fcntl_init(void)
 {
 	/* please add new bits here to ensure allocation uniqueness */
-	BUILD_BUG_ON(18 != HWEIGHT32(
+	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	|