lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

[PATCH] fix race in __block_prepare_write

Browse Source 
Fix a race where __block_prepare_write can leak out an in-flight read
against a bh if get_block returns an error.  This can lead to the page
becoming unlocked while the buffer is locked and the read still in flight.
__mpage_writepage BUGs on this condition.

BUG sighted on a 2-way Itanium2 system with 16K PAGE_SIZE running

	fsstress -v -d $DIR/tmp -n 1000 -p 1000 -l 2

where $DIR is a new ext2 filesystem with 4K blocks that is quite
small (causing get_block to fail often with -ENOSPC).

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin
2005-05-05 16:15:45 -07:00
committed by Linus Torvalds
parent 3c8fad1829
commit f3ddbdc626
1 changed files with 6 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
fs/buffer.c
View File

@@ -1953,7 +1953,7 @@ static int __block_prepare_write(struct inode *inode, struct page *page,
if (!buffer_mapped(bh)) { if (!buffer_mapped(bh)) {
err = get_block(inode, block, bh, 1); err = get_block(inode, block, bh, 1);
if (err) if (err)
goto out; break;
if (buffer_new(bh)) { if (buffer_new(bh)) {
clear_buffer_new(bh); clear_buffer_new(bh);
unmap_underlying_metadata(bh->b_bdev, unmap_underlying_metadata(bh->b_bdev,
@@ -1995,10 +1995,12 @@ static int __block_prepare_write(struct inode *inode, struct page *page,
while(wait_bh > wait) { while(wait_bh > wait) {
wait_on_buffer(*--wait_bh); wait_on_buffer(*--wait_bh);
if (!buffer_uptodate(*wait_bh)) if (!buffer_uptodate(*wait_bh))
return -EIO; err = -EIO;
} }
return 0; if (!err)
out: return err;
/* Error case: */
/* /*
* Zero out any newly allocated blocks to avoid exposing stale * Zero out any newly allocated blocks to avoid exposing stale
* data. If BH_New is set, we know that the block was newly * data. If BH_New is set, we know that the block was newly