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[198.145.29.99]) by mx.google.com with ESMTPS id 91si11159772plh.398.2019.06.01.06.17.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 01 Jun 2019 06:17:46 -0700 (PDT) Received-SPF: pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=PIAJLMrq; spf=pass (google.com: domain of sashal@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=sashal@kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9E3E22569E; Sat, 1 Jun 2019 13:17:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1559395066; bh=SKeFZxLlJJEe28gVBbpYOeHuIKrn5SXSvLw4bDj5xSs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=PIAJLMrqXO9fV6XF4DxT8NsqjxvNxdDm4szh7RUueQN2p+OUWJOay3OaEdcZA9X4N 0aNZcqx7Crw5EtqBRYtGOYIRok0QAcC9DnyaKU2ZufxW3oz3t7DiN2RV5NL8R9CQ2A /LqzE2boG0UYW2tfsyfkVzYMI5q6+2Wxo5bJISfo= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Qian Cai , Vlastimil Babka , Mel Gorman , Andrew Morton , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 5.1 017/186] mm/compaction.c: fix an undefined behaviour Date: Sat, 1 Jun 2019 09:13:53 -0400 Message-Id: <20190601131653.24205-17-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190601131653.24205-1-sashal@kernel.org> References: <20190601131653.24205-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Qian Cai [ Upstream commit dd7ef7bd14640f11763b54f55131000165f48321 ] 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 Acked-by: Vlastimil Babka Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/compaction.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index 444029da4e9d8..7b48ac9164a89 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; } /* -- 2.20.1