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[157.230.128.187]) by smtp.gmail.com with ESMTPSA id u186sm42297pfu.205.2020.04.09.14.45.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Apr 2020 14:45:32 -0700 (PDT) Received: by 42.do-not-panic.com (Postfix, from userid 1000) id 4DC0C41D00; Thu, 9 Apr 2020 21:45:32 +0000 (UTC) From: Luis Chamberlain To: axboe@kernel.dk, viro@zeniv.linux.org.uk, gregkh@linuxfoundation.org, rostedt@goodmis.org, mingo@redhat.com, jack@suse.cz, ming.lei@redhat.com, nstange@suse.de, akpm@linux-foundation.org Cc: mhocko@suse.com, yukuai3@huawei.com, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Luis Chamberlain , Bart Van Assche , Omar Sandoval , Hannes Reinecke , Michal Hocko Subject: [RFC v2 3/5] blktrace: ref count the request_queue during ioctl Date: Thu, 9 Apr 2020 21:45:28 +0000 Message-Id: <20200409214530.2413-4-mcgrof@kernel.org> X-Mailer: git-send-email 2.23.0.rc1 In-Reply-To: <20200409214530.2413-1-mcgrof@kernel.org> References: <20200409214530.2413-1-mcgrof@kernel.org> MIME-Version: 1.0 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: Ensure that the reqest_queue ref counts the request_queue during its full ioctl cycle. This avoids possible races against removal, given blk_get_queue() also checks to ensure the queue is not dying. This small race is possible if you defer removal of the reqest_queue and userspace fires off an ioctl for the device in the meantime. Cc: Bart Van Assche Cc: Omar Sandoval Cc: Hannes Reinecke Cc: Nicolai Stange Cc: Greg Kroah-Hartman Cc: Michal Hocko Cc: yu kuai Signed-off-by: Luis Chamberlain Reviewed-by: Bart Van Assche --- kernel/trace/blktrace.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 15086227592f..17e144d15779 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -701,6 +701,9 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg) if (!q) return -ENXIO; + if (!blk_get_queue(q)) + return -ENXIO; + mutex_lock(&q->blk_trace_mutex); switch (cmd) { @@ -729,6 +732,9 @@ int blk_trace_ioctl(struct block_device *bdev, unsigned cmd, char __user *arg) } mutex_unlock(&q->blk_trace_mutex); + + blk_put_queue(q); + return ret; }