This is a note to let you know that I've just added the patch titled
bcache: fix BUG_ON due to integer overflow with GC_SECTORS_USED
to the 3.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bcache-fix-bug_on-due-to-integer-overflow-with-gc_sectors_used.patch
and it can be found in the queue-3.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 947174476701fbc84ea8c7ec9664270f9d80b076 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
Date: Tue, 28 Jan 2014 16:57:39 -0800
Subject: bcache: fix BUG_ON due to integer overflow with GC_SECTORS_USED
From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Kent Overstreet <kmo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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));
}
Patches currently in stable-queue which might be from darrick.wong@xxxxxxxxxx are
queue-3.13/bcache-fix-bug_on-due-to-integer-overflow-with-gc_sectors_used.patch
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