From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 15 Mar 2021 15:18:48 +0000 From: "Dr. David Alan Gilbert" Message-ID: References: <20210312141003.819108-1-groug@kaod.org> <20210312141003.819108-4-groug@kaod.org> <20210314233604.GC223210@redhat.com> <20210315110630.5ae99490@bahia.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210315110630.5ae99490@bahia.lan> Subject: Re: [Virtio-fs] [PATCH 3/3] virtiofsd: Don't allow empty filenames List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Greg Kurz Cc: virtio-fs@redhat.com, qemu-devel@nongnu.org, Vivek Goyal * Greg Kurz (groug@kaod.org) wrote: > On Sun, 14 Mar 2021 19:36:04 -0400 > Vivek Goyal wrote: > > > On Fri, Mar 12, 2021 at 03:10:03PM +0100, Greg Kurz wrote: > > > POSIX.1-2017 clearly stipulates that empty filenames aren't > > > allowed ([1] and [2]). Since virtiofsd is supposed to mirror > > > the host file system hierarchy and the host can be assumed to > > > be linux, we don't really expect clients to pass requests with > > > an empty path in it. If they do so anyway, this would eventually > > > cause an error when trying to create/lookup the actual inode > > > on the underlying POSIX filesystem. But this could still confuse > > > some code that wouldn't be ready to cope with this. > > > > > > Filter out empty names coming from the client at the top level, > > > so that the rest doesn't have to care about it. This is done > > > everywhere we already call is_safe_path_component(), but > > > in a separate helper since the usual error for empty path > > > names is ENOENT instead of EINVAL. > > > > > > [1] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_170 > > > [2] https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13 > > > > > > Signed-off-by: Greg Kurz > > > > Hi Greg, > > > > Minor nit, if you happen to respin this patch, it probably should come > > before the first patch in series. Once we make it clear that file server > > is not expecting empty path in these top level functions, then it is > > easy to clear AT_EMPTY_PATH in function these paths are calling as > > appropriate. > > > > The patch order is chronological : I just spotted the AT_EMPTY_PATH > oddity before coming up with the bigger hammer of patch 3. But you're > right, it probably makes more sense to do the other way around. > > > What about lo_create(). Should we put a check in there as well. > > > > Good catch ! I'll post a v2 then ;) I'm just brewing a pull now, since soft freeze is tomorrow. I'll take 3,1,2 - please follow up with a separate lo_create one - we can add that later. Dave > > We are passed xattr names in lo_getxattr()/lo_removexattr()/lo_setxattr(). > > In general, should we put an empty in_name check there as well and > > probably simply return -EINVAL. > > > > An empty xattr name doesn't likely make sense either, even if this > isn't written down anywhere, not in an explicit manner at least. > > The kernel checks this in setxattr() and errors out with -ERANGE > in this case. > > error = strncpy_from_user(kname, name, sizeof(kname)); > if (error == 0 || error == sizeof(kname)) > error = -ERANGE; > if (error < 0) > return error; > > Same goes for the other *xattr() syscalls, i.e. nothing nasty can ever > happen with an empty xattr name since this is always considered as an > error by the kernel. Not sure this would bring much to also check this > in QEMU. This is a bit different from the empty path name case because > an empty path name is valid for syscalls that support AT_EMPTY_PATH, > and we just want to make sure these are never exercised with names > from the client. > > Cheers, > > -- > Greg > > > Thanks > > Vivek > > > > > --- > > > tools/virtiofsd/passthrough_ll.c | 35 ++++++++++++++++++++++++++++++++ > > > 1 file changed, 35 insertions(+) > > > > > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > > > index f63016d35626..bff9dc2cd26d 100644 > > > --- a/tools/virtiofsd/passthrough_ll.c > > > +++ b/tools/virtiofsd/passthrough_ll.c > > > @@ -237,6 +237,11 @@ static bool is_safe_path_component(const char *path) > > > return !is_dot_or_dotdot(path); > > > } > > > > > > +static bool is_empty(const char *name) > > > +{ > > > + return name[0] == '\0'; > > > +} > > > + > > > static struct lo_data *lo_data(fuse_req_t req) > > > { > > > return (struct lo_data *)fuse_req_userdata(req); > > > @@ -1083,6 +1088,11 @@ static void lo_lookup(fuse_req_t req, fuse_ino_t parent, const char *name) > > > fuse_log(FUSE_LOG_DEBUG, "lo_lookup(parent=%" PRIu64 ", name=%s)\n", parent, > > > name); > > > > > > + if (is_empty(name)) { > > > + fuse_reply_err(req, ENOENT); > > > + return; > > > + } > > > + > > > /* > > > * Don't use is_safe_path_component(), allow "." and ".." for NFS export > > > * support. > > > @@ -1174,6 +1184,11 @@ static void lo_mknod_symlink(fuse_req_t req, fuse_ino_t parent, > > > struct fuse_entry_param e; > > > struct lo_cred old = {}; > > > > > > + if (is_empty(name)) { > > > + fuse_reply_err(req, ENOENT); > > > + return; > > > + } > > > + > > > if (!is_safe_path_component(name)) { > > > fuse_reply_err(req, EINVAL); > > > return; > > > @@ -1246,6 +1261,11 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent, > > > char procname[64]; > > > int saverr; > > > > > > + if (is_empty(name)) { > > > + fuse_reply_err(req, ENOENT); > > > + return; > > > + } > > > + > > > if (!is_safe_path_component(name)) { > > > fuse_reply_err(req, EINVAL); > > > return; > > > @@ -1323,6 +1343,11 @@ static void lo_rmdir(fuse_req_t req, fuse_ino_t parent, const char *name) > > > struct lo_inode *inode; > > > struct lo_data *lo = lo_data(req); > > > > > > + if (is_empty(name)) { > > > + fuse_reply_err(req, ENOENT); > > > + return; > > > + } > > > + > > > if (!is_safe_path_component(name)) { > > > fuse_reply_err(req, EINVAL); > > > return; > > > @@ -1352,6 +1377,11 @@ static void lo_rename(fuse_req_t req, fuse_ino_t parent, const char *name, > > > struct lo_inode *newinode = NULL; > > > struct lo_data *lo = lo_data(req); > > > > > > + if (is_empty(name) || is_empty(newname)) { > > > + fuse_reply_err(req, ENOENT); > > > + return; > > > + } > > > + > > > if (!is_safe_path_component(name) || !is_safe_path_component(newname)) { > > > fuse_reply_err(req, EINVAL); > > > return; > > > @@ -1405,6 +1435,11 @@ static void lo_unlink(fuse_req_t req, fuse_ino_t parent, const char *name) > > > struct lo_inode *inode; > > > struct lo_data *lo = lo_data(req); > > > > > > + if (is_empty(name)) { > > > + fuse_reply_err(req, ENOENT); > > > + return; > > > + } > > > + > > > if (!is_safe_path_component(name)) { > > > fuse_reply_err(req, EINVAL); > > > return; > > > -- > > > 2.26.2 > > > > > > _______________________________________________ > > > Virtio-fs mailing list > > > Virtio-fs@redhat.com > > > https://listman.redhat.com/mailman/listinfo/virtio-fs > > > > _______________________________________________ > Virtio-fs mailing list > Virtio-fs@redhat.com > https://listman.redhat.com/mailman/listinfo/virtio-fs -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK