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| author | Eric Biggers <ebiggers@google.com> | 2017-11-16 01:38:09 +0100 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2017-11-16 22:49:57 +0100 |
| commit | 74d4108d9e681dbbe4a2940ed8fdff1f6868184c (patch) | |
| tree | a6fff902641076e347609e31cfe9fa293ef32cf9 /Documentation | |
| parent | dm: clear all discard attributes in queue_limits when discards are disabled (diff) | |
| download | linux-74d4108d9e681dbbe4a2940ed8fdff1f6868184c.tar.xz linux-74d4108d9e681dbbe4a2940ed8fdff1f6868184c.zip | |
dm bufio: fix integer overflow when limiting maximum cache size
The default max_cache_size_bytes for dm-bufio is meant to be the lesser
of 25% of the size of the vmalloc area and 2% of the size of lowmem.
However, on 32-bit systems the intermediate result in the expression
(VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100
overflows, causing the wrong result to be computed. For example, on a
32-bit system where the vmalloc area is 520093696 bytes, the result is
1174405 rather than the expected 130023424, which makes the maximum
cache size much too small (far less than 2% of lowmem). This causes
severe performance problems for dm-verity users on affected systems.
Fix this by using mult_frac() to correctly multiply by a percentage. Do
this for all places in dm-bufio that multiply by a percentage. Also
replace (VMALLOC_END - VMALLOC_START) with VMALLOC_TOTAL, which contrary
to the comment is now defined in include/linux/vmalloc.h.
Depends-on: 9993bc635 ("sched/x86: Fix overflow in cyc2ns_offset")
Fixes: 95d402f057f2 ("dm: add bufio")
Cc: <stable@vger.kernel.org> # v3.2+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Diffstat (limited to 'Documentation')
0 files changed, 0 insertions, 0 deletions