Commit 67935df4 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Al Viro
Browse files

[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: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 82666020

fs/proc/generic.c

+9 −12
Original line number Original line Diff line number Diff line
@@ -303,7 +303,7 @@ out: 
static DEFINE_IDR(proc_inum_idr);

static DEFINE_IDR(proc_inum_idr);

static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */

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

 * 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)

static unsigned int get_inode_number(void)

{

{

	int i, inum = 0;

	unsigned int i;

	int error;

	int error;





retry:

retry:
@@ -326,21 +326,18 @@ retry: 
	else if (error)

	else if (error)

		return 0;

		return 0;





	inum = (i & MAX_ID_MASK) + PROC_DYNAMIC_FIRST;

	if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {



		spin_lock(&proc_inum_lock);

	/* inum will never be more than 0xf0ffffff, so no check

		idr_remove(&proc_inum_idr, i);

	 * for overflow.

		spin_unlock(&proc_inum_lock);

	 */

	}



	return PROC_DYNAMIC_FIRST + i;

	return inum;

}

}





static void release_inode_number(unsigned int inum)

static void release_inode_number(unsigned int inum)

{

{

	int id = (inum - PROC_DYNAMIC_FIRST) | ~MAX_ID_MASK;



	spin_lock(&proc_inum_lock);

	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);

	spin_unlock(&proc_inum_lock);

}

}

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