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spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:57388 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jeEyA-0004MY-96 for qemu-devel@archiver.kernel.org; Thu, 28 May 2020 05:36:58 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:36822) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jeEx5-0003JG-5i for qemu-devel@nongnu.org; Thu, 28 May 2020 05:35:51 -0400 Received: from mout.kundenserver.de ([212.227.126.131]:43067) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jeEx4-0003QX-9m for qemu-devel@nongnu.org; Thu, 28 May 2020 05:35:50 -0400 Received: from [192.168.100.1] ([82.252.135.106]) by mrelayeu.kundenserver.de (mreue012 [213.165.67.103]) with ESMTPSA (Nemesis) id 1MumVX-1imYAZ0rKN-00rpNo; Thu, 28 May 2020 11:35:48 +0200 Subject: Re: [PATCH] linux-user/mmap.c: fix integer underflow in target_mremap To: Jonathan Marler , qemu-devel@nongnu.org References: <20200502161225.14346-1-johnnymarler@gmail.com> From: Laurent Vivier Autocrypt: addr=laurent@vivier.eu; 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envelope-from=laurent@vivier.eu; helo=mout.kundenserver.de X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/28 05:34:18 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Le 02/05/2020 à 18:12, Jonathan Marler a écrit : > Fixes: https://bugs.launchpad.net/bugs/1876373 > > This code path in mmap occurs when a page size is decreased with mremap. When a section of pages is shrunk, qemu calls mmap_reserve on the pages that were released. However, it has the diff operation reversed, subtracting the larger old_size from the smaller new_size. Instead, it should be subtracting the smaller new_size from the larger old_size. You can also see in the previous line of the change that this mmap_reserve call only occurs when old_size > new_size. > > Signed-off-by: Jonathan Marler > --- > linux-user/mmap.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/linux-user/mmap.c b/linux-user/mmap.c > index e378033797..caab62909e 100644 > --- a/linux-user/mmap.c > +++ b/linux-user/mmap.c > @@ -708,7 +708,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size, > if (prot == 0) { > host_addr = mremap(g2h(old_addr), old_size, new_size, flags); > if (host_addr != MAP_FAILED && reserved_va && old_size > new_size) { > - mmap_reserve(old_addr + old_size, new_size - old_size); > + mmap_reserve(old_addr + old_size, old_size - new_size); > } > } else { > errno = ENOMEM; > Applied to my linux-user branch. Thanks, Laurent