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[PATCH 1/2] proc: fix inode number bogorithmetic 

Id which proc gets from IDR for inode number and id which proc removes
from IDR do not match. E.g. 0x11a transforms into 0x8000011a.

Which stayed unnoticed for a long time because, surprise, idr_remove()
masks out that high bit before doing anything.

All of this due to "| ~MAX_ID_MASK" in release_inode_number().

I still don't understand how it's supposed to work, because "| ~MASK"
is not an inversion for "& MAX" operation.

So, use just one nice, working addition. Make start offset unsigned int,
while I'm at it. It's longness is not used anywhere.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Alexey Dobriyan 2008-07-26 11:18:28 +04:00 committed by Al Viro
parent 8266602033
commit 67935df49d
1 changed files with 9 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
fs/proc/generic.c
View File

@ -303,7 +303,7 @@ static int xlate_proc_name(const char *name,
static DEFINE_IDR(proc_inum_idr);
static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */
#define PROC_DYNAMIC_FIRST 0xF0000000UL
#define PROC_DYNAMIC_FIRST 0xF0000000U
/*
* Return an inode number between PROC_DYNAMIC_FIRST and
@ -311,7 +311,7 @@ static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */
*/
static unsigned int get_inode_number(void)
{
int i, inum = 0;
unsigned int i;
int error;
retry:
@ -326,21 +326,18 @@ static unsigned int get_inode_number(void)
else if (error)
return 0;
inum = (i & MAX_ID_MASK) + PROC_DYNAMIC_FIRST;
/* inum will never be more than 0xf0ffffff, so no check
* for overflow.
*/
return inum;
if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {
spin_lock(&proc_inum_lock);
idr_remove(&proc_inum_idr, i);
spin_unlock(&proc_inum_lock);
}
return PROC_DYNAMIC_FIRST + i;
}
static void release_inode_number(unsigned int inum)
{
int id = (inum - PROC_DYNAMIC_FIRST) | ~MAX_ID_MASK;
spin_lock(&proc_inum_lock);
idr_remove(&proc_inum_idr, id);
idr_remove(&proc_inum_idr, inum - PROC_DYNAMIC_FIRST);
spin_unlock(&proc_inum_lock);
}