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([2601:647:4000:d7:8ef:746a:4fe7:1df]) by smtp.gmail.com with ESMTPSA id c4sm4526784pga.73.2020.05.09.17.58.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 09 May 2020 17:58:57 -0700 (PDT) Subject: Re: [PATCH v4 3/5] blktrace: fix debugfs use after free To: Luis Chamberlain , 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, Omar Sandoval , Hannes Reinecke , Michal Hocko , Christof Schmitt , syzbot+603294af2d01acfdd6da@syzkaller.appspotmail.com References: <20200509031058.8239-1-mcgrof@kernel.org> <20200509031058.8239-4-mcgrof@kernel.org> From: Bart Van Assche Autocrypt: addr=bvanassche@acm.org; prefer-encrypt=mutual; keydata= mQENBFSOu4oBCADcRWxVUvkkvRmmwTwIjIJvZOu6wNm+dz5AF4z0FHW2KNZL3oheO3P8UZWr LQOrCfRcK8e/sIs2Y2D3Lg/SL7qqbMehGEYcJptu6mKkywBfoYbtBkVoJ/jQsi2H0vBiiCOy fmxMHIPcYxaJdXxrOG2UO4B60Y/BzE6OrPDT44w4cZA9DH5xialliWU447Bts8TJNa3lZKS1 AvW1ZklbvJfAJJAwzDih35LxU2fcWbmhPa7EO2DCv/LM1B10GBB/oQB5kvlq4aA2PSIWkqz4 3SI5kCPSsygD6wKnbRsvNn2mIACva6VHdm62A7xel5dJRfpQjXj2snd1F/YNoNc66UUTABEB AAG0JEJhcnQgVmFuIEFzc2NoZSA8YnZhbmFzc2NoZUBhY20ub3JnPokBOQQTAQIAIwUCVI67 igIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEHFcPTXFzhAJ8QkH/1AdXblKL65M Y1Zk1bYKnkAb4a98LxCPm/pJBilvci6boefwlBDZ2NZuuYWYgyrehMB5H+q+Kq4P0IBbTqTa jTPAANn62A6jwJ0FnCn6YaM9TZQjM1F7LoDX3v+oAkaoXuq0dQ4hnxQNu792bi6QyVdZUvKc macVFVgfK9n04mL7RzjO3f+X4midKt/s+G+IPr4DGlrq+WH27eDbpUR3aYRk8EgbgGKvQFdD CEBFJi+5ZKOArmJVBSk21RHDpqyz6Vit3rjep7c1SN8s7NhVi9cjkKmMDM7KYhXkWc10lKx2 RTkFI30rkDm4U+JpdAd2+tP3tjGf9AyGGinpzE2XY1K5AQ0EVI67igEIAKiSyd0nECrgz+H5 PcFDGYQpGDMTl8MOPCKw/F3diXPuj2eql4xSbAdbUCJzk2ETif5s3twT2ER8cUTEVOaCEUY3 eOiaFgQ+nGLx4BXqqGewikPJCe+UBjFnH1m2/IFn4T9jPZkV8xlkKmDUqMK5EV9n3eQLkn5g lco+FepTtmbkSCCjd91EfThVbNYpVQ5ZjdBCXN66CKyJDMJ85HVr5rmXG/nqriTh6cv1l1Js T7AFvvPjUPknS6d+BETMhTkbGzoyS+sywEsQAgA+BMCxBH4LvUmHYhpS+W6CiZ3ZMxjO8Hgc ++w1mLeRUvda3i4/U8wDT3SWuHcB3DWlcppECLkAEQEAAYkBHwQYAQIACQUCVI67igIbDAAK CRBxXD01xc4QCZ4dB/0QrnEasxjM0PGeXK5hcZMT9Eo998alUfn5XU0RQDYdwp6/kMEXMdmT oH0F0xB3SQ8WVSXA9rrc4EBvZruWQ+5/zjVrhhfUAx12CzL4oQ9Ro2k45daYaonKTANYG22y //x8dLe2Fv1By4SKGhmzwH87uXxbTJAUxiWIi1np0z3/RDnoVyfmfbbL1DY7zf2hYXLLzsJR mSsED/1nlJ9Oq5fALdNEPgDyPUerqHxcmIub+pF0AzJoYHK5punqpqfGmqPbjxrJLPJfHVKy goMj5DlBMoYqEgpbwdUYkH6QdizJJCur4icy8GUNbisFYABeoJ91pnD4IGei3MTdvINSZI5e Message-ID: <16fe176f-1dbd-d14c-bfc2-5aee1ca8c64e@acm.org> Date: Sat, 9 May 2020 17:58:55 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200509031058.8239-4-mcgrof@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 2020-05-08 20:10, Luis Chamberlain wrote: > Screenshots of what the debugfs for block looks like after running > blktrace on a system with sg0 which has a raid controllerand then sg1 > as the media changer: > > # ls -l /sys/kernel/debug/block > total 0 > drwxr-xr-x 3 root root 0 May 9 02:31 bsg > drwxr-xr-x 19 root root 0 May 9 02:31 nvme0n1 > drwxr-xr-x 19 root root 0 May 9 02:31 nvme1n1 > lrwxrwxrwx 1 root root 0 May 9 02:31 nvme1n1p1 -> nvme1n1 > lrwxrwxrwx 1 root root 0 May 9 02:31 nvme1n1p2 -> nvme1n1 > lrwxrwxrwx 1 root root 0 May 9 02:31 nvme1n1p3 -> nvme1n1 > lrwxrwxrwx 1 root root 0 May 9 02:31 nvme1n1p5 -> nvme1n1 > lrwxrwxrwx 1 root root 0 May 9 02:31 nvme1n1p6 -> nvme1n1 > drwxr-xr-x 2 root root 0 May 9 02:33 sch0 > lrwxrwxrwx 1 root root 0 May 9 02:33 sg0 -> bsg/2:0:0:0 > lrwxrwxrwx 1 root root 0 May 9 02:33 sg1 -> sch0 > drwxr-xr-x 5 root root 0 May 9 02:31 vda > lrwxrwxrwx 1 root root 0 May 9 02:31 vda1 -> vda So this patch creates one soft link per partition at partition creation time instead of letting the blktrace code create one directory per partition when tracing starts? Does this break running blktrace simultaneously for a partition and for the entire block device? > +static struct dentry *queue_debugfs_symlink_type(struct request_queue *q, > + const char *src, > + const char *dst, > + enum blk_debugfs_dir_type type) > +{ > + struct dentry *dentry = ERR_PTR(-EINVAL); > + char *dir_dst; > + > + dir_dst = kzalloc(PATH_MAX, GFP_KERNEL); > + if (!dir_dst) > + return dentry; > + > + switch (type) { > + case BLK_DBG_DIR_BASE: > + if (dst) > + snprintf(dir_dst, PATH_MAX, "%s", dst); > + else if (!IS_ERR_OR_NULL(q->debugfs_dir)) > + snprintf(dir_dst, PATH_MAX, "%s", > + q->debugfs_dir->d_name.name); > + else > + goto out; > + break; > + case BLK_DBG_DIR_BSG: > + if (dst) > + snprintf(dir_dst, PATH_MAX, "bsg/%s", dst); > + else > + goto out; > + break; > + } > + > + /* > + * The base block debugfs directory is always used for the symlinks, > + * their target is what changes. > + */ > + dentry = debugfs_create_symlink(src, blk_debugfs_root, dir_dst); > +out: > + kfree(dir_dst); > + > + return dentry; > +} Please use kasprintf() instead of k?alloc() followed by snprintf(). Thanks, Bart.