From: Mel Gorman <mgorman@techsingularity.net>
To: Qian Cai <cai@lca.pw>
Cc: akpm@linux-foundation.org, vbabka@suse.cz, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/compaction: fix an undefined behaviour
Date: Sat, 9 Mar 2019 00:28:41 +0000 [thread overview]
Message-ID: <20190309002841.GL9565@techsingularity.net> (raw)
In-Reply-To: <20190308224650.68955-1-cai@lca.pw>
On Fri, Mar 08, 2019 at 05:46:50PM -0500, Qian Cai wrote:
> 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
>
> Fixes: 70b44595eafe ("mm, compaction: use free lists to quickly locate a migration source")
> Signed-off-by: Qian Cai <cai@lca.pw>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
FWIW, I had seen the same message when trying to isolate potential
corruption (still unsuccessful, the tests always complete) but
considered it relatively benign and harmless. Still worth fixing so
thanks.
--
Mel Gorman
SUSE Labs
prev parent reply other threads:[~2019-03-09 0:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-08 22:46 [PATCH] mm/compaction: fix an undefined behaviour Qian Cai
2019-03-09 0:28 ` Mel Gorman [this message]
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