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| author | Darrick J. Wong <darrick.wong@oracle.com> | 2014-01-28 16:57:39 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-02-20 11:10:11 -0800 |
| commit | b8bb5472da4bf66da971acb7a923f8a7e58420a7 (patch) | |
| tree | cdd967a9ed98c96e7d5a0161e95c2307a4537119 | |
| parent | 75fd721996e2ebf32c469bc39687b425b7a00d90 (diff) | |
| download | lwn-b8bb5472da4bf66da971acb7a923f8a7e58420a7.tar.gz lwn-b8bb5472da4bf66da971acb7a923f8a7e58420a7.zip | |
bcache: fix BUG_ON due to integer overflow with GC_SECTORS_USED
commit 947174476701fbc84ea8c7ec9664270f9d80b076 upstream.
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>
Cc: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/md/bcache/bcache.h | 4 | ||||
| -rw-r--r-- | drivers/md/bcache/btree.c | 2 |
2 files changed, 4 insertions, 2 deletions
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 754f43177483..cf3f6f897f1b 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -209,7 +209,9 @@ 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 31bb53fcc67a..7966ff827680 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1163,7 +1163,7 @@ 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)); } |