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Thu, 22 Oct 2020 12:16:56 -0400 (EDT) Date: Thu, 22 Oct 2020 12:16:56 -0400 From: Vivek Goyal To: "Dr. David Alan Gilbert (git)" Subject: Re: [PATCH v3 3/5] tools/virtiofsd: xattr name mappings: Map server xattr names Message-ID: <20201022161656.GD512900@redhat.com> References: <20201014180209.49299-1-dgilbert@redhat.com> <20201014180209.49299-4-dgilbert@redhat.com> MIME-Version: 1.0 In-Reply-To: <20201014180209.49299-4-dgilbert@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vgoyal@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=vgoyal@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/22 08:33:10 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, 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: dinechin@redhat.com, virtio-fs@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Oct 14, 2020 at 07:02:07PM +0100, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > Map xattr names coming from the server, i.e. the host filesystem; > currently this is only from listxattr. > > Signed-off-by: Dr. David Alan Gilbert > --- > tools/virtiofsd/passthrough_ll.c | 89 ++++++++++++++++++++++++++++++++ > 1 file changed, 89 insertions(+) > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 57ebe17ed6..8406a2ae86 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -2220,6 +2220,43 @@ static int xattr_map_client(const struct lo_data *lo, const char *client_name, > } > } > > + /* Shouldn't get here - rules should have an END_* - check parse_xattrmap */ > + abort(); > +} > + > +/* > + * For use with listxattr where the server fs gives us a name and we may need > + * to sanitize this for the client. > + * Returns a pointer to the result in *out_name > + * This is always the original string or the current string with some prefix > + * removed; no reallocation is done. > + * Returns 0 on success > + * Can return -ENODATA to indicate the name should be dropped from the list. > + */ > +static int xattr_map_server(const struct lo_data *lo, const char *server_name, > + const char **out_name) > +{ > + const XattrMapEntry *cur_entry; > + const char *end; > + > + for (cur_entry = lo->xattr_map_list; ; cur_entry++) { > + if ((cur_entry->flags & XATTR_MAP_FLAG_SERVER) && > + (strstart(server_name, cur_entry->prepend, &end))) { > + if (cur_entry->flags & XATTR_MAP_FLAG_END_BAD) { > + return -ENODATA; > + } > + if (cur_entry->flags & XATTR_MAP_FLAG_END_OK) { > + *out_name = server_name; > + return 0; > + } > + if (cur_entry->flags & XATTR_MAP_FLAG_PREFIX) { > + /* Remove prefix */ > + *out_name = end; > + return 0; > + } > + } > + } > + > /* Shouldn't get here - rules should have an END_* */ > abort(); I am wondering why to put that restriction. If none of the rules match, can't we just return as nothing has to be done. > } > @@ -2378,8 +2415,60 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) > if (ret == 0) { > goto out; > } > + > + if (lo->xattr_map_list) { > + /* > + * Map the names back, some attributes might be dropped, > + * some shortened, but not increased, so we shouldn't > + * run out of room. > + */ > + size_t out_index, in_index; > + out_index = 0; > + in_index = 0; > + while (in_index < ret) { > + const char *map_out; > + char *in_ptr = value + in_index; > + /* Length of current attribute name */ > + size_t in_len = strlen(value + in_index) + 1; > + > + int mapret = xattr_map_server(lo, in_ptr, &map_out); > + if (mapret != -ENODATA && mapret != 0) { > + /* Shouldn't happen */ > + saverr = -mapret; > + goto out; > + } > + if (mapret == 0) { > + /* Either unchanged, or truncated */ > + size_t out_len; > + if (map_out != in_ptr) { > + /* +1 copies the NIL */ > + out_len = strlen(map_out) + 1; > + } else { > + /* No change */ > + out_len = in_len; > + } > + /* > + * Move result along, may still be needed for an unchanged > + * entry if a previous entry was changed. > + */ > + memmove(value + out_index, map_out, out_len); > + > + out_index += out_len; > + } > + in_index += in_len; > + } > + ret = out_index; > + if (ret == 0) { > + goto out; > + } > + } > fuse_reply_buf(req, value, ret); > } else { > + /* > + * xattrmap only ever shortens the result, > + * so we don't need to do anything clever with the > + * allocation length here. > + */ > fuse_reply_xattr(req, ret); Hmmm.., so this code returns the length of buffer which will fit xattrs. So we will will changing the semantics a bit. Instead of returning the exact size of buffer needed, we will be returning max size. I hope its not a problem. Fixing it will be too expensive I guess. Thanks Vivek From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 22 Oct 2020 12:16:56 -0400 From: Vivek Goyal Message-ID: <20201022161656.GD512900@redhat.com> References: <20201014180209.49299-1-dgilbert@redhat.com> <20201014180209.49299-4-dgilbert@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201014180209.49299-4-dgilbert@redhat.com> Subject: Re: [Virtio-fs] [PATCH v3 3/5] tools/virtiofsd: xattr name mappings: Map server xattr names List-Id: Development discussions about virtio-fs List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" Cc: dinechin@redhat.com, virtio-fs@redhat.com, qemu-devel@nongnu.org On Wed, Oct 14, 2020 at 07:02:07PM +0100, Dr. David Alan Gilbert (git) wrote: > From: "Dr. David Alan Gilbert" > > Map xattr names coming from the server, i.e. the host filesystem; > currently this is only from listxattr. > > Signed-off-by: Dr. David Alan Gilbert > --- > tools/virtiofsd/passthrough_ll.c | 89 ++++++++++++++++++++++++++++++++ > 1 file changed, 89 insertions(+) > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 57ebe17ed6..8406a2ae86 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -2220,6 +2220,43 @@ static int xattr_map_client(const struct lo_data *lo, const char *client_name, > } > } > > + /* Shouldn't get here - rules should have an END_* - check parse_xattrmap */ > + abort(); > +} > + > +/* > + * For use with listxattr where the server fs gives us a name and we may need > + * to sanitize this for the client. > + * Returns a pointer to the result in *out_name > + * This is always the original string or the current string with some prefix > + * removed; no reallocation is done. > + * Returns 0 on success > + * Can return -ENODATA to indicate the name should be dropped from the list. > + */ > +static int xattr_map_server(const struct lo_data *lo, const char *server_name, > + const char **out_name) > +{ > + const XattrMapEntry *cur_entry; > + const char *end; > + > + for (cur_entry = lo->xattr_map_list; ; cur_entry++) { > + if ((cur_entry->flags & XATTR_MAP_FLAG_SERVER) && > + (strstart(server_name, cur_entry->prepend, &end))) { > + if (cur_entry->flags & XATTR_MAP_FLAG_END_BAD) { > + return -ENODATA; > + } > + if (cur_entry->flags & XATTR_MAP_FLAG_END_OK) { > + *out_name = server_name; > + return 0; > + } > + if (cur_entry->flags & XATTR_MAP_FLAG_PREFIX) { > + /* Remove prefix */ > + *out_name = end; > + return 0; > + } > + } > + } > + > /* Shouldn't get here - rules should have an END_* */ > abort(); I am wondering why to put that restriction. If none of the rules match, can't we just return as nothing has to be done. > } > @@ -2378,8 +2415,60 @@ static void lo_listxattr(fuse_req_t req, fuse_ino_t ino, size_t size) > if (ret == 0) { > goto out; > } > + > + if (lo->xattr_map_list) { > + /* > + * Map the names back, some attributes might be dropped, > + * some shortened, but not increased, so we shouldn't > + * run out of room. > + */ > + size_t out_index, in_index; > + out_index = 0; > + in_index = 0; > + while (in_index < ret) { > + const char *map_out; > + char *in_ptr = value + in_index; > + /* Length of current attribute name */ > + size_t in_len = strlen(value + in_index) + 1; > + > + int mapret = xattr_map_server(lo, in_ptr, &map_out); > + if (mapret != -ENODATA && mapret != 0) { > + /* Shouldn't happen */ > + saverr = -mapret; > + goto out; > + } > + if (mapret == 0) { > + /* Either unchanged, or truncated */ > + size_t out_len; > + if (map_out != in_ptr) { > + /* +1 copies the NIL */ > + out_len = strlen(map_out) + 1; > + } else { > + /* No change */ > + out_len = in_len; > + } > + /* > + * Move result along, may still be needed for an unchanged > + * entry if a previous entry was changed. > + */ > + memmove(value + out_index, map_out, out_len); > + > + out_index += out_len; > + } > + in_index += in_len; > + } > + ret = out_index; > + if (ret == 0) { > + goto out; > + } > + } > fuse_reply_buf(req, value, ret); > } else { > + /* > + * xattrmap only ever shortens the result, > + * so we don't need to do anything clever with the > + * allocation length here. > + */ > fuse_reply_xattr(req, ret); Hmmm.., so this code returns the length of buffer which will fit xattrs. So we will will changing the semantics a bit. Instead of returning the exact size of buffer needed, we will be returning max size. I hope its not a problem. Fixing it will be too expensive I guess. Thanks Vivek