From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6F8E6C433E0 for ; Fri, 15 May 2020 14:11:46 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3951B2075F for ; Fri, 15 May 2020 14:11:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Poy2XC8j" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3951B2075F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:54520 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jZb3x-0005lP-D6 for qemu-devel@archiver.kernel.org; Fri, 15 May 2020 10:11:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33100) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jZb3M-0005JT-1v for qemu-devel@nongnu.org; Fri, 15 May 2020 10:11:08 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:46345 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1jZb3L-0001Jx-0L for qemu-devel@nongnu.org; Fri, 15 May 2020 10:11:07 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589551865; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=5ypat35HJiZdr6QubaMI7QE5CF0ac3OiJ+WUL1mSSV0=; b=Poy2XC8jv/jpEHqrI5rDMUL8vNdFkZIDPHsAew3YTIfU8utuF9T2jwF8YZHVauaVyjtOtv dUo75LC/NQJ6VPnfw3vsNXdnUg4wcWiriEW98jrgHsaam7bpwWFZUI/qjHavgsd8X8GG2n m9Qbo9Y3mEUE/qusG8AEsKnVUC3Cvhw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-21-N1NiQMlTNUyqBHRDSKq_yg-1; Fri, 15 May 2020 10:11:02 -0400 X-MC-Unique: N1NiQMlTNUyqBHRDSKq_yg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D21B28005AD for ; Fri, 15 May 2020 14:11:01 +0000 (UTC) Received: from horse.redhat.com (ovpn-114-113.rdu2.redhat.com [10.10.114.113]) by smtp.corp.redhat.com (Postfix) with ESMTP id A53F312A4D; Fri, 15 May 2020 14:10:58 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 0B85B220206; Fri, 15 May 2020 10:10:58 -0400 (EDT) Date: Fri, 15 May 2020 10:10:57 -0400 From: Vivek Goyal To: Miklos Szeredi Subject: Re: [Virtio-fs] [PATCH] virtiofsd: remove symlink fallbacks Message-ID: <20200515141057.GB235744@redhat.com> References: <20200514140736.20561-1-mszeredi@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200514140736.20561-1-mszeredi@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 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=207.211.31.120; envelope-from=vgoyal@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/14 22:56:02 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_H2=-0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN 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, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, May 14, 2020 at 04:07:36PM +0200, Miklos Szeredi wrote: > Path lookup in the kernel has special rules for looking up magic symlinks > under /proc. If a filesystem operation is instructed to follow symlinks > (e.g. via AT_SYMLINK_FOLLOW or lack of AT_SYMLINK_NOFOLLOW), and the final > component is such a proc symlink, then the target of the magic symlink is > used for the operation, even if the target itself is a symlink. I.e. path > lookup is always terminated after following a final magic symlink. > > I was erronously assuming that in the above case the target symlink would > also be followed, and so workarounds were added for a couple of operations > to handle the symlink case. Since the symlink can be handled simply by > following the proc symlink, these workardouds are not needed. > > Also remove the "norace" option, which disabled the workarounds. > > Commit bdfd66788349 ("virtiofsd: Fix xattr operations") already dealt with > the same issue for xattr operations. > > Signed-off-by: Miklos Szeredi Good to have this cleanup. Acked-by: Vivek Goyal Vivek > --- > tools/virtiofsd/passthrough_ll.c | 175 ++----------------------------- > 1 file changed, 6 insertions(+), 169 deletions(-) > > diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c > index 3ba1d9098460..2ce7c96085bf 100644 > --- a/tools/virtiofsd/passthrough_ll.c > +++ b/tools/virtiofsd/passthrough_ll.c > @@ -140,7 +140,6 @@ enum { > struct lo_data { > pthread_mutex_t mutex; > int debug; > - int norace; > int writeback; > int flock; > int posix_lock; > @@ -176,7 +175,6 @@ static const struct fuse_opt lo_opts[] = { > { "cache=none", offsetof(struct lo_data, cache), CACHE_NONE }, > { "cache=auto", offsetof(struct lo_data, cache), CACHE_AUTO }, > { "cache=always", offsetof(struct lo_data, cache), CACHE_ALWAYS }, > - { "norace", offsetof(struct lo_data, norace), 1 }, > { "readdirplus", offsetof(struct lo_data, readdirplus_set), 1 }, > { "no_readdirplus", offsetof(struct lo_data, readdirplus_clear), 1 }, > FUSE_OPT_END > @@ -592,136 +590,6 @@ static void lo_getattr(fuse_req_t req, fuse_ino_t ino, > fuse_reply_attr(req, &buf, lo->timeout); > } > > -/* > - * Increments parent->nlookup and caller must release refcount using > - * lo_inode_put(&parent). > - */ > -static int lo_parent_and_name(struct lo_data *lo, struct lo_inode *inode, > - char path[PATH_MAX], struct lo_inode **parent) > -{ > - char procname[64]; > - char *last; > - struct stat stat; > - struct lo_inode *p; > - int retries = 2; > - int res; > - > -retry: > - sprintf(procname, "%i", inode->fd); > - > - res = readlinkat(lo->proc_self_fd, procname, path, PATH_MAX); > - if (res < 0) { > - fuse_log(FUSE_LOG_WARNING, "%s: readlink failed: %m\n", __func__); > - goto fail_noretry; > - } > - > - if (res >= PATH_MAX) { > - fuse_log(FUSE_LOG_WARNING, "%s: readlink overflowed\n", __func__); > - goto fail_noretry; > - } > - path[res] = '\0'; > - > - last = strrchr(path, '/'); > - if (last == NULL) { > - /* Shouldn't happen */ > - fuse_log( > - FUSE_LOG_WARNING, > - "%s: INTERNAL ERROR: bad path read from proc\n", __func__); > - goto fail_noretry; > - } > - if (last == path) { > - p = &lo->root; > - pthread_mutex_lock(&lo->mutex); > - p->nlookup++; > - g_atomic_int_inc(&p->refcount); > - pthread_mutex_unlock(&lo->mutex); > - } else { > - *last = '\0'; > - res = fstatat(AT_FDCWD, last == path ? "/" : path, &stat, 0); > - if (res == -1) { > - if (!retries) { > - fuse_log(FUSE_LOG_WARNING, > - "%s: failed to stat parent: %m\n", __func__); > - } > - goto fail; > - } > - p = lo_find(lo, &stat); > - if (p == NULL) { > - if (!retries) { > - fuse_log(FUSE_LOG_WARNING, > - "%s: failed to find parent\n", __func__); > - } > - goto fail; > - } > - } > - last++; > - res = fstatat(p->fd, last, &stat, AT_SYMLINK_NOFOLLOW); > - if (res == -1) { > - if (!retries) { > - fuse_log(FUSE_LOG_WARNING, > - "%s: failed to stat last\n", __func__); > - } > - goto fail_unref; > - } > - if (stat.st_dev != inode->key.dev || stat.st_ino != inode->key.ino) { > - if (!retries) { > - fuse_log(FUSE_LOG_WARNING, > - "%s: failed to match last\n", __func__); > - } > - goto fail_unref; > - } > - *parent = p; > - memmove(path, last, strlen(last) + 1); > - > - return 0; > - > -fail_unref: > - unref_inode_lolocked(lo, p, 1); > - lo_inode_put(lo, &p); > -fail: > - if (retries) { > - retries--; > - goto retry; > - } > -fail_noretry: > - errno = EIO; > - return -1; > -} > - > -static int utimensat_empty(struct lo_data *lo, struct lo_inode *inode, > - const struct timespec *tv) > -{ > - int res; > - struct lo_inode *parent; > - char path[PATH_MAX]; > - > - if (S_ISLNK(inode->filetype)) { > - res = utimensat(inode->fd, "", tv, AT_EMPTY_PATH); > - if (res == -1 && errno == EINVAL) { > - /* Sorry, no race free way to set times on symlink. */ > - if (lo->norace) { > - errno = EPERM; > - } else { > - goto fallback; > - } > - } > - return res; > - } > - sprintf(path, "%i", inode->fd); > - > - return utimensat(lo->proc_self_fd, path, tv, 0); > - > -fallback: > - res = lo_parent_and_name(lo, inode, path, &parent); > - if (res != -1) { > - res = utimensat(parent->fd, path, tv, AT_SYMLINK_NOFOLLOW); > - unref_inode_lolocked(lo, parent, 1); > - lo_inode_put(lo, &parent); > - } > - > - return res; > -} > - > static int lo_fi_fd(fuse_req_t req, struct fuse_file_info *fi) > { > struct lo_data *lo = lo_data(req); > @@ -828,7 +696,8 @@ static void lo_setattr(fuse_req_t req, fuse_ino_t ino, struct stat *attr, > if (fi) { > res = futimens(fd, tv); > } else { > - res = utimensat_empty(lo, inode, tv); > + sprintf(procname, "%i", inode->fd); > + res = utimensat(lo->proc_self_fd, procname, tv, 0); > } > if (res == -1) { > goto out_err; > @@ -1129,41 +998,6 @@ static void lo_symlink(fuse_req_t req, const char *link, fuse_ino_t parent, > lo_mknod_symlink(req, parent, name, S_IFLNK, 0, link); > } > > -static int linkat_empty_nofollow(struct lo_data *lo, struct lo_inode *inode, > - int dfd, const char *name) > -{ > - int res; > - struct lo_inode *parent; > - char path[PATH_MAX]; > - > - if (S_ISLNK(inode->filetype)) { > - res = linkat(inode->fd, "", dfd, name, AT_EMPTY_PATH); > - if (res == -1 && (errno == ENOENT || errno == EINVAL)) { > - /* Sorry, no race free way to hard-link a symlink. */ > - if (lo->norace) { > - errno = EPERM; > - } else { > - goto fallback; > - } > - } > - return res; > - } > - > - sprintf(path, "%i", inode->fd); > - > - return linkat(lo->proc_self_fd, path, dfd, name, AT_SYMLINK_FOLLOW); > - > -fallback: > - res = lo_parent_and_name(lo, inode, path, &parent); > - if (res != -1) { > - res = linkat(parent->fd, path, dfd, name, 0); > - unref_inode_lolocked(lo, parent, 1); > - lo_inode_put(lo, &parent); > - } > - > - return res; > -} > - > static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent, > const char *name) > { > @@ -1172,6 +1006,7 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent, > struct lo_inode *parent_inode; > struct lo_inode *inode; > struct fuse_entry_param e; > + char procname[64]; > int saverr; > > if (!is_safe_path_component(name)) { > @@ -1190,7 +1025,9 @@ static void lo_link(fuse_req_t req, fuse_ino_t ino, fuse_ino_t parent, > e.attr_timeout = lo->timeout; > e.entry_timeout = lo->timeout; > > - res = linkat_empty_nofollow(lo, inode, parent_inode->fd, name); > + sprintf(procname, "%i", inode->fd); > + res = linkat(lo->proc_self_fd, procname, parent_inode->fd, name, > + AT_SYMLINK_FOLLOW); > if (res == -1) { > goto out_err; > } > -- > 2.21.1 > > _______________________________________________ > Virtio-fs mailing list > Virtio-fs@redhat.com > https://www.redhat.com/mailman/listinfo/virtio-fs