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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>
This commit is contained in:
Jan Kara 2010-08-19 14:13:33 -07:00 committed by Linus Torvalds
parent f2e41e9103
commit d5ed3a4af7
2 changed files with 6 additions and 2 deletions
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5
lib/radix-tree.c
View File

@ -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;

3
mm/page-writeback.c
View File

@ -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);