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[157.230.128.187]) by smtp.gmail.com with ESMTPSA id c1sm539415pfo.197.2020.06.05.15.33.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Jun 2020 15:33:21 -0700 (PDT) Received: by 42.do-not-panic.com (Postfix, from userid 1000) id 8E4B8403AB; Fri, 5 Jun 2020 22:33:20 +0000 (UTC) Date: Fri, 5 Jun 2020 22:33:20 +0000 From: Luis Chamberlain To: Bart Van Assche Cc: Christoph Hellwig , 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, 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, Omar Sandoval , Hannes Reinecke , Michal Hocko , syzbot+603294af2d01acfdd6da@syzkaller.appspotmail.com Subject: Re: [PATCH v5 5/7] blktrace: fix debugfs use after free Message-ID: <20200605223320.GN11244@42.do-not-panic.com> References: <20200516031956.2605-1-mcgrof@kernel.org> <20200516031956.2605-6-mcgrof@kernel.org> <20200519163713.GA29944@infradead.org> <20200527031202.GT11244@42.do-not-panic.com> <20200601170500.GF13911@42.do-not-panic.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Queue-Id: 070C81804E3A0 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 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, Jun 04, 2020 at 09:48:43PM -0700, Bart Van Assche wrote: > On 2020-06-01 10:05, Luis Chamberlain wrote: > > diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c > > index a55cbfd060f5..5b0310f38e11 100644 > > --- a/kernel/trace/blktrace.c > > +++ b/kernel/trace/blktrace.c > > @@ -511,6 +511,11 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev, > > */ > > if (bdev && bdev != bdev->bd_contains) { > > dir = bdev->bd_part->debugfs_dir; > > + } else if (q->sg_debugfs_dir && > > + strlen(buts->name) == strlen(q->sg_debugfs_dir->d_name.name) > > + && strcmp(buts->name, q->sg_debugfs_dir->d_name.name) == 0) { > > + /* scsi-generic requires use of its own directory */ > > + dir = q->sg_debugfs_dir; > > } else { > > /* > > * For queues that do not have a gendisk attached to them, that > > > > Please Cc Martin Petersen for patches that modify SCSI code. Sure thing. > The string comparison check looks fragile to me. Is the purpose of that > check perhaps to verify whether tracing is being activated through the > SCSI generic interface? Yes. > If so, how about changing that test into > something like the following? > > MAJOR(dev) == SCSI_GENERIC_MAJOR Sure. Luis