Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.13 38/40] bcache: fix BUG_ON due to integer overflow with GC_SECTORS_USED | Date | Tue, 18 Feb 2014 14:47:39 -0800 |
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3.13-stable review patch. If anyone has any objections, please let me know.
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From: "Darrick J. Wong" <darrick.wong@oracle.com>
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>
--- drivers/md/bcache/bcache.h | 4 +++- drivers/md/bcache/btree.c | 2 +- 2 files changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -209,7 +209,9 @@ BITMASK(GC_MARK, struct bucket, gc_mark #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" --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1163,7 +1163,7 @@ uint8_t __bch_btree_mark_key(struct cach /* 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)); }
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