* [PATCH] fs: fix integer overflow in MS_NOUSER definition
@ 2012-04-21 5:49 Konstantin Khlebnikov
2012-04-21 6:28 ` Al Viro
0 siblings, 1 reply; 3+ messages in thread
From: Konstantin Khlebnikov @ 2012-04-21 5:49 UTC (permalink / raw)
To: linux-fsdevel, linux-kernel; +Cc: Alexander Viro
MS_NOUSER defined as signed int (1<<31), sb->s_flags declared as unsigned long.
So (sb->s_flags & MS_NOUSER) works as (sb->s_flags & 0xffffffff80000000).
Other potential bugs: git grep -w -e '1\s*<<\s*31'
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
---
include/linux/fs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6b71bd6..903bf00 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -217,7 +217,7 @@ struct inodes_stat_t {
#define MS_NOSEC (1<<28)
#define MS_BORN (1<<29)
#define MS_ACTIVE (1<<30)
-#define MS_NOUSER (1<<31)
+#define MS_NOUSER (1u<<31)
/*
* Superblock flags that can be altered by MS_REMOUNT
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] fs: fix integer overflow in MS_NOUSER definition
2012-04-21 5:49 [PATCH] fs: fix integer overflow in MS_NOUSER definition Konstantin Khlebnikov
@ 2012-04-21 6:28 ` Al Viro
2012-04-21 8:37 ` Konstantin Khlebnikov
0 siblings, 1 reply; 3+ messages in thread
From: Al Viro @ 2012-04-21 6:28 UTC (permalink / raw)
To: Konstantin Khlebnikov; +Cc: linux-fsdevel, linux-kernel
On Sat, Apr 21, 2012 at 09:49:49AM +0400, Konstantin Khlebnikov wrote:
> MS_NOUSER defined as signed int (1<<31), sb->s_flags declared as unsigned long.
> So (sb->s_flags & MS_NOUSER) works as (sb->s_flags & 0xffffffff80000000).
... and it's not a problem since we can't use bits 32 and above anyway -
unsigned long is 32bit on a lot of platforms. I have no objections to
making that 1U<<31, but it's not a bug, let alone an integer overflow.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] fs: fix integer overflow in MS_NOUSER definition
2012-04-21 6:28 ` Al Viro
@ 2012-04-21 8:37 ` Konstantin Khlebnikov
0 siblings, 0 replies; 3+ messages in thread
From: Konstantin Khlebnikov @ 2012-04-21 8:37 UTC (permalink / raw)
To: Al Viro; +Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Al Viro wrote:
> On Sat, Apr 21, 2012 at 09:49:49AM +0400, Konstantin Khlebnikov wrote:
>> MS_NOUSER defined as signed int (1<<31), sb->s_flags declared as unsigned long.
>> So (sb->s_flags& MS_NOUSER) works as (sb->s_flags& 0xffffffff80000000).
>
> ... and it's not a problem since we can't use bits 32 and above anyway -
> unsigned long is 32bit on a lot of platforms. I have no objections to
> making that 1U<<31, but it's not a bug, let alone an integer overflow.
Yes, it's not a bug here, but I not sure about the rest thousand places, where
similar expressions are used. Probably checkpatch should warn about such things.
BTW this patch makes code smaller =)
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-16 (-16)
function old new delta
graft_tree 135 119 -16
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-04-21 5:49 [PATCH] fs: fix integer overflow in MS_NOUSER definition Konstantin Khlebnikov
2012-04-21 6:28 ` Al Viro
2012-04-21 8:37 ` Konstantin Khlebnikov
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