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[68.103.222.6]) by smtp.gmail.com with ESMTPSA id z14sm428999oid.12.2021.03.12.07.13.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Mar 2021 07:13:38 -0800 (PST) Subject: Re: [Virtio-fs] [PATCH 1/3] virtiofsd: Don't allow empty paths in lookup_name() To: Greg Kurz , qemu-devel@nongnu.org References: <20210312141003.819108-1-groug@kaod.org> <20210312141003.819108-2-groug@kaod.org> From: Connor Kuehl Message-ID: Date: Fri, 12 Mar 2021 09:13:36 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20210312141003.819108-2-groug@kaod.org> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ckuehl@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=ckuehl@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.25, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: , Cc: virtio-fs@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/12/21 8:10 AM, Greg Kurz wrote: > When passed an empty filename, lookup_name() returns the inode of > the parent directory, unless the parent is the root in which case > the st_dev doesn't match and lo_find() returns NULL. This is > because lookup_name() passes AT_EMPTY_PATH down to fstatat() or > statx(). > > This behavior doesn't quite make sense because users of lookup_name() > then pass the name to unlinkat(), renameat() or renameat2(), all of > which will always fail on empty names. > > Drop AT_EMPTY_PATH from the flags in lookup_name() so that it has > the consistent behavior of "returning an existing child inode or > NULL" for all directories. > > Signed-off-by: Greg Kurz > --- > tools/virtiofsd/passthrough_ll.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index fc7e1b1e8e2b..27a6c636dcaf 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -1308,8 +1308,7 @@ static struct lo_inode *lookup_name(fuse_req_t req, fuse_ino_t parent, > return NULL; > } > > - res = do_statx(lo, dir->fd, name, &attr, > - AT_EMPTY_PATH | AT_SYMLINK_NOFOLLOW, &mnt_id); > + res = do_statx(lo, dir->fd, name, &attr, AT_SYMLINK_NOFOLLOW, &mnt_id); > lo_inode_put(lo, &dir); > if (res == -1) { > return NULL; > Should the statx() in lo_do_lookup() have this flag removed as well? I don't think its callers will pass in an empty name because: - One of your later patches prevents lo_mknod_symlink() from doing so - lo_create() will fail an earlier call against the host file system (open) - lo_do_readdir() shouldn't be reading empty names because that implies someone was able to pull off making an entry with an empty name However, I don't know if there will one day be future callers to lo_do_lookup() that will depend on that flag. If the answer to the above is no, then: Reviewed-by: Connor Kuehl