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| author | Qian Cai <cai@lca.pw> | 2019-05-13 17:17:38 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-05-14 09:47:46 -0700 |
| commit | dd7ef7bd14640f11763b54f55131000165f48321 (patch) | |
| tree | c8b42e3dac6653da76bfa814b77d5cf85a757f81 /mm/compaction.c | |
| parent | d3ba3ae19751e476b0840a0c9a673a5766fa3219 (diff) | |
| download | lwn-dd7ef7bd14640f11763b54f55131000165f48321.tar.gz lwn-dd7ef7bd14640f11763b54f55131000165f48321.zip | |
mm/compaction.c: fix an undefined behaviour
In a low-memory situation, cc->fast_search_fail can keep increasing as it
is unable to find an available page to isolate in
fast_isolate_freepages(). As the result, it could trigger an error below,
so just compare with the maximum bits can be shifted first.
UBSAN: Undefined behaviour in mm/compaction.c:1160:30
shift exponent 64 is too large for 64-bit type 'unsigned long'
CPU: 131 PID: 1308 Comm: kcompactd1 Kdump: loaded Tainted: G
W L 5.0.0+ #17
Call trace:
dump_backtrace+0x0/0x450
show_stack+0x20/0x2c
dump_stack+0xc8/0x14c
__ubsan_handle_shift_out_of_bounds+0x7e8/0x8c4
compaction_alloc+0x2344/0x2484
unmap_and_move+0xdc/0x1dbc
migrate_pages+0x274/0x1310
compact_zone+0x26ec/0x43bc
kcompactd+0x15b8/0x1a24
kthread+0x374/0x390
ret_from_fork+0x10/0x18
[akpm@linux-foundation.org: code cleanup]
Link: http://lkml.kernel.org/r/20190320203338.53367-1-cai@lca.pw
Fixes: 70b44595eafe ("mm, compaction: use free lists to quickly locate a migration source")
Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/compaction.c')
| -rw-r--r-- | mm/compaction.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/mm/compaction.c b/mm/compaction.c index 3319e0872d01..6cc4bea33dcb 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1164,7 +1164,9 @@ static bool suitable_migration_target(struct compact_control *cc, static inline unsigned int freelist_scan_limit(struct compact_control *cc) { - return (COMPACT_CLUSTER_MAX >> cc->fast_search_fail) + 1; + unsigned short shift = BITS_PER_LONG - 1; + + return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1; } /* |