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authorQian Cai <cai@lca.pw>2019-05-13 17:17:38 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-14 09:47:46 -0700
commitdd7ef7bd14640f11763b54f55131000165f48321 (patch)
treec8b42e3dac6653da76bfa814b77d5cf85a757f81 /mm
parentd3ba3ae19751e476b0840a0c9a673a5766fa3219 (diff)
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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')
-rw-r--r--mm/compaction.c4
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;
}
/*