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Tue, 22 Jun 2021 19:03:09 +0000 Received: from aserp3020.oracle.com (aserp3020.oracle.com [127.0.0.1]) by pps.reinject (8.16.0.36/8.16.0.36) with SMTP id 15MJ30SH034073; Tue, 22 Jun 2021 19:03:09 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by aserp3020.oracle.com with ESMTP id 3998d7xhf4-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 22 Jun 2021 19:03:09 +0000 Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 15MJ36UJ032204; Tue, 22 Jun 2021 19:03:06 GMT Received: from mwanda (/102.222.70.252) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 22 Jun 2021 12:03:06 -0700 Date: Tue, 22 Jun 2021 22:03:00 +0300 From: Dan Carpenter To: Andrew Morton , Alistair Popple Cc: Stephen Rothwell , linux-mm@kvack.org, kernel-janitors@vger.kernel.org Subject: [PATCH] mm/rmap: fix signedness bug in make_device_exclusive_range() Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Mailer: git-send-email haha only kidding X-Proofpoint-ORIG-GUID: jdHkRmqOmiF1sAW5D8WZXwgl5SZdej6p X-Proofpoint-GUID: jdHkRmqOmiF1sAW5D8WZXwgl5SZdej6p Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2020-01-29 header.b=I4gUDbSd; spf=none (imf10.hostedemail.com: domain of dan.carpenter@oracle.com has no SPF policy when checking 205.220.165.32) smtp.mailfrom=dan.carpenter@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: CFA134000394 X-Stat-Signature: 3n8awp3muok1s8y6bo3znk7o98x8cs6n X-HE-Tag: 1624388603-30417 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: The get_user_pages_remote() function returns a long type, but we are using "unsigned long i;" as the list iterator. If "npages" is -ENOMEM, the comparison "i < npages" is type promoted and "npages" becomes a very high positive value. The loop will then iterate until the kernel crashes. There are two ways to fix this. Declare "i" as a long type or add an explicit check for get_user_pages_remote() error returns. Either approach will work so let's do both. Fixes: fa1e686e5f53 ("mm: device exclusive memory access") Signed-off-by: Dan Carpenter --- mm/rmap.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/rmap.c b/mm/rmap.c index e5210dde0c4d..fb5c59b95826 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -2187,11 +2187,14 @@ int make_device_exclusive_range(struct mm_struct *mm, unsigned long start, void *owner) { long npages = (end - start) >> PAGE_SHIFT; - unsigned long i; + long i; npages = get_user_pages_remote(mm, start, npages, FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD, pages, NULL, NULL); + if (npages < 0) + return npages; + for (i = 0; i < npages; i++, start += PAGE_SIZE) { if (!trylock_page(pages[i])) { put_page(pages[i]); -- 2.30.2