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authorDarrick J. Wong <darrick.wong@oracle.com>2014-01-28 16:57:39 -0800
committerKent Overstreet <kmo@daterainc.com>2014-01-29 13:06:15 -0800
commit947174476701fbc84ea8c7ec9664270f9d80b076 (patch)
tree285c85c76652bbdf42ac9adb7a82a662ddc9dd65 /drivers/md
parent9dd6358a21daf4fc6a5b2b779267a62f0d1d3181 (diff)
bcache: fix BUG_ON due to integer overflow with GC_SECTORS_USED
The BUG_ON at the end of __bch_btree_mark_key can be triggered due to an integer overflow error: BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, 13); ... SET_GC_SECTORS_USED(g, min_t(unsigned, GC_SECTORS_USED(g) + KEY_SIZE(k), (1 << 14) - 1)); BUG_ON(!GC_SECTORS_USED(g)); In bcache.h, the SECTORS_USED bitfield is defined to be 13 bits wide. While the SET_ code tries to ensure that the field doesn't overflow by clamping it to (1<<14)-1 == 16383, this is incorrect because 16383 requires 14 bits. Therefore, if GC_SECTORS_USED() + KEY_SIZE() = 8192, the SET_ statement tries to store 8192 into a 13-bit field. In a 13-bit field, 8192 becomes zero, thus triggering the BUG_ON. Therefore, create a field width constant and a max value constant, and use those to create the bitfield and check the inputs to SET_GC_SECTORS_USED. Arguably the BITMASK() template ought to have BUG_ON checks for too-large values, but that's a separate patch. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/bcache/bcache.h4
-rw-r--r--drivers/md/bcache/btree.c2
2 files changed, 4 insertions, 2 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 0c707e4f4ea..a4c7306ff43 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -210,7 +210,9 @@ BITMASK(GC_MARK, struct bucket, gc_mark, 0, 2);
#define GC_MARK_RECLAIMABLE 0
#define GC_MARK_DIRTY 1
#define GC_MARK_METADATA 2
-BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, 13);
+#define GC_SECTORS_USED_SIZE 13
+#define MAX_GC_SECTORS_USED (~(~0ULL << GC_SECTORS_USED_SIZE))
+BITMASK(GC_SECTORS_USED, struct bucket, gc_mark, 2, GC_SECTORS_USED_SIZE);
BITMASK(GC_MOVE, struct bucket, gc_mark, 15, 1);
#include "journal.h"
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index 98cc0a810a3..7d421180b6d 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -1167,7 +1167,7 @@ uint8_t __bch_btree_mark_key(struct cache_set *c, int level, struct bkey *k)
/* guard against overflow */
SET_GC_SECTORS_USED(g, min_t(unsigned,
GC_SECTORS_USED(g) + KEY_SIZE(k),
- (1 << 14) - 1));
+ MAX_GC_SECTORS_USED));
BUG_ON(!GC_SECTORS_USED(g));
}