Commit dfd20b2b authored May 24, 2013 by Brian Behlendorf Committed by Linus Torvalds May 24, 2013

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>

parent e5ee7305

drivers/block/brd.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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();

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