From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f200.google.com (mail-pg1-f200.google.com [209.85.215.200]) by kanga.kvack.org (Postfix) with ESMTP id 434836B0006 for ; Tue, 13 Nov 2018 19:51:50 -0500 (EST) Received: by mail-pg1-f200.google.com with SMTP id l131so9489971pga.2 for ; Tue, 13 Nov 2018 16:51:50 -0800 (PST) Received: from smtp.codeaurora.org (smtp.codeaurora.org. [198.145.29.96]) by mx.google.com with ESMTPS id x15-v6si21980538pll.41.2018.11.13.16.51.48 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 13 Nov 2018 16:51:49 -0800 (PST) From: "Isaac J. Manjarres" Subject: [PATCH] mm/usercopy: Use memory range to be accessed for wraparound check Date: Tue, 13 Nov 2018 16:51:26 -0800 Message-Id: <1542156686-12253-1-git-send-email-isaacm@codeaurora.org> Sender: owner-linux-mm@kvack.org List-ID: To: keescook@chromium.org, crecklin@redhat.com Cc: "Isaac J. Manjarres" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, psodagud@codeaurora.org, tsoni@codeaurora.org, stable@vger.kernel.org Currently, when checking to see if accessing n bytes starting at address "ptr" will cause a wraparound in the memory addresses, the check in check_bogus_address() adds an extra byte, which is incorrect, as the range of addresses that will be accessed is [ptr, ptr + (n - 1)]. This can lead to incorrectly detecting a wraparound in the memory address, when trying to read 4 KB from memory that is mapped to the the last possible page in the virtual address space, when in fact, accessing that range of memory would not cause a wraparound to occur. Use the memory range that will actually be accessed when considering if accessing a certain amount of bytes will cause the memory address to wrap around. Change-Id: I2563a5988e41122727ede17180f365e999b953e6 Fixes: f5509cc18daa ("mm: Hardened usercopy") Co-Developed-by: Prasad Sodagudi Signed-off-by: Prasad Sodagudi Signed-off-by: Isaac J. Manjarres Cc: stable@vger.kernel.org --- mm/usercopy.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/usercopy.c b/mm/usercopy.c index 852eb4e..0293645 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -151,7 +151,7 @@ static inline void check_bogus_address(const unsigned long ptr, unsigned long n, bool to_user) { /* Reject if object wraps past end of memory. */ - if (ptr + n < ptr) + if (ptr + (n - 1) < ptr) usercopy_abort("wrapped address", NULL, to_user, 0, ptr + n); /* Reject if NULL or ZERO-allocation. */ -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project