From: Brian Behlendorf <behlendorf1@xxxxxxxx>
Subject: 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@xxxxxxxx>
Reported-by: Chris Wedgwood <cw@xxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/brd.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN drivers/block/brd.c~drivers-block-brdc-fix-brd_lookup_page-race drivers/block/brd.c
--- a/drivers/block/brd.c~drivers-block-brdc-fix-brd_lookup_page-race
+++ a/drivers/block/brd.c
@@ -117,13 +117,13 @@ static struct page *brd_insert_page(stru
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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