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| author | Eric Biggers <ebiggers@google.com> | 2017-11-15 16:38:09 -0800 |
|---|---|---|
| committer | Mike Snitzer <snitzer@redhat.com> | 2017-11-16 16:49:57 -0500 |
| commit | 74d4108d9e681dbbe4a2940ed8fdff1f6868184c (patch) | |
| tree | a6fff902641076e347609e31cfe9fa293ef32cf9 /drivers | |
| parent | 5d47c89f29eab6e9e224d7ac8c0baf4da72c9493 (diff) | |
| download | linux-74d4108d9e681dbbe4a2940ed8fdff1f6868184c.tar.bz2 | |
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 'drivers')
| -rw-r--r-- | drivers/md/dm-bufio.c | 15 |
1 files changed, 6 insertions, 9 deletions
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index d216a8f7bc22..8e3adcb46851 100644 --- a/drivers/md/dm-bufio.c +++ b/drivers/md/dm-bufio.c @@ -974,7 +974,8 @@ static void __get_memory_limit(struct dm_bufio_client *c, buffers = c->minimum_buffers; *limit_buffers = buffers; - *threshold_buffers = buffers * DM_BUFIO_WRITEBACK_PERCENT / 100; + *threshold_buffers = mult_frac(buffers, + DM_BUFIO_WRITEBACK_PERCENT, 100); } /* @@ -1910,19 +1911,15 @@ static int __init dm_bufio_init(void) memset(&dm_bufio_caches, 0, sizeof dm_bufio_caches); memset(&dm_bufio_cache_names, 0, sizeof dm_bufio_cache_names); - mem = (__u64)((totalram_pages - totalhigh_pages) * - DM_BUFIO_MEMORY_PERCENT / 100) << PAGE_SHIFT; + mem = (__u64)mult_frac(totalram_pages - totalhigh_pages, + DM_BUFIO_MEMORY_PERCENT, 100) << PAGE_SHIFT; if (mem > ULONG_MAX) mem = ULONG_MAX; #ifdef CONFIG_MMU - /* - * Get the size of vmalloc space the same way as VMALLOC_TOTAL - * in fs/proc/internal.h - */ - if (mem > (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100) - mem = (VMALLOC_END - VMALLOC_START) * DM_BUFIO_VMALLOC_PERCENT / 100; + if (mem > mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100)) + mem = mult_frac(VMALLOC_TOTAL, DM_BUFIO_VMALLOC_PERCENT, 100); #endif dm_bufio_default_cache_size = mem; |