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drivers/block/brd.c: fix brd_lookup_page() race 

The index on the page must be set before it is inserted in the radix
tree.  Otherwise there is a small race which can occur during lookup
where the page can be found with the incorrect index.  This will trigger
the BUG_ON() in brd_lookup_page().

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reported-by: Chris Wedgwood <cw@f00f.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Brian Behlendorf 2013-05-24 15:55:28 -07:00 committed by Linus Torvalds
parent e5ee7305ae
commit dfd20b2b17
1 changed files with 2 additions and 2 deletions
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4
drivers/block/brd.c
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@ -117,13 +117,13 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
spin_lock(&brd->brd_lock);
idx = sector >> PAGE_SECTORS_SHIFT;
page->index = idx;
if (radix_tree_insert(&brd->brd_pages, idx, page)) {
__free_page(page);
page = radix_tree_lookup(&brd->brd_pages, idx);
BUG_ON(!page);
BUG_ON(page->index != idx);
} else
page->index = idx;
}
spin_unlock(&brd->brd_lock);
radix_tree_preload_end();