diff options
| author | Jan Kara <jack@suse.cz> | 2010-08-19 14:13:33 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-08-20 09:34:55 -0700 |
| commit | d5ed3a4af77b851b6271ad3d9abc4c57fa3ce0f5 (patch) | |
| tree | f06894404e4af25051e8918bfd3fdac95974fc97 | |
| parent | f2e41e910320197d55b52e28d99a07130f2ae738 (diff) | |
lib/radix-tree.c: fix overflow in radix_tree_range_tag_if_tagged()
When radix_tree_maxindex() is ~0UL, it can happen that scanning overflows
index and tree traversal code goes astray reading memory until it hits
unreadable memory. Check for overflow and exit in that case.
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | lib/radix-tree.c | 5 | ||||
| -rw-r--r-- | mm/page-writeback.c | 3 |
2 files changed, 6 insertions, 2 deletions
diff --git a/lib/radix-tree.c b/lib/radix-tree.c index e907858498a6..5b7d4623f0b7 100644 --- a/lib/radix-tree.c +++ b/lib/radix-tree.c @@ -625,6 +625,8 @@ EXPORT_SYMBOL(radix_tree_tag_get); * * The function returns number of leaves where the tag was set and sets * *first_indexp to the first unscanned index. + * WARNING! *first_indexp can wrap if last_index is ULONG_MAX. Caller must + * be prepared to handle that. */ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, unsigned long *first_indexp, unsigned long last_index, @@ -675,7 +677,8 @@ unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root, next: /* Go to next item at level determined by 'shift' */ index = ((index >> shift) + 1) << shift; - if (index > last_index) + /* Overflow can happen when last_index is ~0UL... */ + if (index > last_index || !index) break; if (tagged >= nr_to_tag) break; diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 7262aacea8a2..c09ef5219cbe 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -836,7 +836,8 @@ void tag_pages_for_writeback(struct address_space *mapping, spin_unlock_irq(&mapping->tree_lock); WARN_ON_ONCE(tagged > WRITEBACK_TAG_BATCH); cond_resched(); - } while (tagged >= WRITEBACK_TAG_BATCH); + /* We check 'start' to handle wrapping when end == ~0UL */ + } while (tagged >= WRITEBACK_TAG_BATCH && start); } EXPORT_SYMBOL(tag_pages_for_writeback); |