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[198.145.29.99]) by mx.google.com with ESMTPS id h99si3128657pje.83.2019.07.18.21.11.09 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 21:11:09 -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=Qo6+nRkj; 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 D682121872; Fri, 19 Jul 2019 04:11:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1563509468; bh=ayNMgFyXiftuip0Uxel5UmXwcABdBHOMaIPv9xzWQSo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Qo6+nRkjkjO/LNYSE9MHCDPglUMV4XD4WsEMR7jOFp5/KIycU6JFUAUqCBgG+Yptz 5oakQhx9R8Ka2GSyIAjZSNqBbKuQIOHoNckgtoCfGnnEFAPrpk2msTUpKQ8CVDOWTZ oR2n9SPwYbXu+l4OrWK4OOHNC7j4RTNfLZCNbM68= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Konstantin Khlebnikov , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Oleg Nesterov , Michal Hocko , Alexey Dobriyan , Matthew Wilcox , Cyrill Gorcunov , Kirill Tkhai , Al Viro , Roman Gushchin , Andrew Morton , Linus Torvalds , Sasha Levin , linux-mm@kvack.org Subject: [PATCH AUTOSEL 4.19 101/101] mm: use down_read_killable for locking mmap_sem in access_remote_vm Date: Fri, 19 Jul 2019 00:07:32 -0400 Message-Id: <20190719040732.17285-101-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190719040732.17285-1-sashal@kernel.org> References: <20190719040732.17285-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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: Konstantin Khlebnikov [ Upstream commit 1e426fe28261b03f297992e89da3320b42816f4e ] This function is used by ptrace and proc files like /proc/pid/cmdline and /proc/pid/environ. Access_remote_vm never returns error codes, all errors are ignored and only size of successfully read data is returned. So, if current task was killed we'll simply return 0 (bytes read). Mmap_sem could be locked for a long time or forever if something goes wrong. Using a killable lock permits cleanup of stuck tasks and simplifies investigation. Link: http://lkml.kernel.org/r/156007494202.3335.16782303099589302087.stgit@buzz Signed-off-by: Konstantin Khlebnikov Reviewed-by: Michal Koutný Acked-by: Oleg Nesterov Acked-by: Michal Hocko Cc: Alexey Dobriyan Cc: Matthew Wilcox Cc: Cyrill Gorcunov Cc: Kirill Tkhai Cc: Al Viro Cc: Roman Gushchin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- mm/memory.c | 4 +++- mm/nommu.c | 3 ++- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index e0010cb870e0..fb5655b518c9 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4491,7 +4491,9 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, void *old_buf = buf; int write = gup_flags & FOLL_WRITE; - down_read(&mm->mmap_sem); + if (down_read_killable(&mm->mmap_sem)) + return 0; + /* ignore errors, just check how much was successfully transferred */ while (len) { int bytes, ret, offset; diff --git a/mm/nommu.c b/mm/nommu.c index e4aac33216ae..1d63ecfc98c5 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -1779,7 +1779,8 @@ int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm, struct vm_area_struct *vma; int write = gup_flags & FOLL_WRITE; - down_read(&mm->mmap_sem); + if (down_read_killable(&mm->mmap_sem)) + return 0; /* the access must start within one of the target process's mappings */ vma = find_vma(mm, addr); -- 2.20.1