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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pO3gs-00Eekg-Sx; Fri, 03 Feb 2023 21:33:50 +0000 Date: Fri, 3 Feb 2023 21:33:50 +0000 From: Matthew Wilcox To: Andrew Morton Cc: mm-commits@vger.kernel.org, ira.weiny@intel.com, fmdefrancesco@gmail.com, linux-mm@kvack.org Subject: Re: [merged mm-stable] mm-add-memcpy_from_file_folio.patch removed from -mm tree Message-ID: References: <20230203063850.3246FC4339C@smtp.kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230203063850.3246FC4339C@smtp.kernel.org> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 60391A0004 X-Rspam-User: X-Stat-Signature: jhntut65buz5s98f6a1nrs7pg86xm9z6 X-HE-Tag: 1675460048-287615 X-HE-Meta: U2FsdGVkX1+ul9h2XCSt4V782obquLibEvhd9OkQUrD61+bjZjtgxHBCGIs0hwYFdflQWsH8mgi4AEbQxhTGPlf5SyVZmraieDAtYeINPTW5SZZSYc3GqpwG5bAWd+1ymO1dvrVLk69qc/i6SywsOkztNAk4AIJ0vrGYWsQFSCMFb2HX4jcf53b4+45mFOQuJFgczUuQ7V0V1XOB1JQnVwiWgBJ5nsYUhsbAaVzCPgq3atcO294oZJV+AqVSlq6oLBjkmX+daQIkypkInmFb7MJJ88n01ei89DdwYKdKtT1wYMaq+XO/Xx31xk+kUwWNWKHtKSOsINLdbWG5u/Dz/y9W/UwSVyE5RiNAqtBuR0mJ4R0k553aqdao1S65TbkmQU8HNC1AHgFIKGe8iXrfuTtVE0TaQ1KTXMfJF9Pfi5PIsaxO9X6QaLtHh54rcM2jRGZuvnvI8oEG+sfFtoeuRuZw0WUSHHsdJvKU4CD5/64QXiQXBhsvDmWZShrp5b0o3WuTuTL5IxWlwEs9jv+PTjonn93rh2I6+Lfn8+4P0VU2iYB+pklcgTwSqQwyMMUxBWfED5RKKBf+C0yi/P+hP6+ALkwi1i8k4ntBqrCvejr9M11h3kIeZrak5Es3jIp9uuZKVAm6mx9E+DMjX8W9uLWddHNiOFxv+DWYou5LftjWKb9MjiBdrplWB53h6yT23H+MBq4qW0zDCavd/x7bkr3yi2bZqMjORRsExjEKZwuymPLuVSzpWNETMXwymL68lln6RjxgOZrc0aEppmReIJR/6O9BAr77kgsIdVUDI8lD0i14QqhXd3VS0G+Ttw3HwHRzTSeABZuXyqERI4ELT9nK5siTuVVi0ewsxjl6sQuUYbCfvlAIGGeVkDfwwj7oKX+94x20TF3Vxe4t3Slvrx9dKjdC12Z/EeBysLZI5BNYv5zmQ5UFxyS4B4Ub8UnAKgnRPUSCJw5gtVq+9+N l4cxU0+w u/+odBMq9lWgEZSa0swyRpyPdoDbcoUgqFsaM2yoOT3j2GtQA5Hl0qzsmS+PTRwO+R7aSp4scUhfd5toqO3yhtUPlwwIQMFBB3Sestlt7Z2+IGHV4bMgHDxdUS3gpTX+QJIO4CIMHTPigvPo0s0H7Q6gjnqZ6txvPU8JsTVm4inf+J4JON5t+UETZUvzd20JGzQvAVP3yGcWBsuh5TrSqOkbdWcwV5ybF0dMZUfuLy6PsiI9VSnPCasGBmJ3lVpftfKqIWOvhxuMqLtRAZTiyNBrzMkE9ht+ZG8n43mnwvlBIe0jbl58sCMbvAU9CM4grGlw9 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: On Thu, Feb 02, 2023 at 10:38:49PM -0800, Andrew Morton wrote: > This patch was dropped because it was merged into the mm-stable branch > of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm I pick the worst time to find bugs in my own code. >From cf8f62107c965eafc2fa9ad0f839269fcb11991d Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Fri, 3 Feb 2023 16:28:40 -0500 Subject: [PATCH] mm: Fix memcpy_from_file_folio() integer underflow If we have a HIGHMEM system with a large folio, 'offset' may be larger than PAGE_SIZE, and so min_t will cap at 'len' instead of the intended end-of-page. That can overflow into the next page which is likely to be unmapped and fault, but could theoretically copy the wrong data. Fixes: [no commit ID yet] ("mm: add memcpy_from_file_folio()") Signed-off-by: Matthew Wilcox (Oracle) --- include/linux/highmem.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/include/linux/highmem.h b/include/linux/highmem.h index 348701dae77f..b06254e76d99 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -431,9 +431,10 @@ static inline size_t memcpy_from_file_folio(char *to, struct folio *folio, size_t offset = offset_in_folio(folio, pos); char *from = kmap_local_folio(folio, offset); - if (folio_test_highmem(folio)) + if (folio_test_highmem(folio)) { + offset = offset_in_page(offset); len = min_t(size_t, len, PAGE_SIZE - offset); - else + } else len = min(len, folio_size(folio) - offset); memcpy(to, from, len); -- 2.35.1