From 2e58ff6978f8433fc8672d2e357c6f0f5f36d24f Mon Sep 17 00:00:00 2001 From: "Dr. David Alan Gilbert" Date: Mon, 27 Jan 2020 19:02:07 +0100 Subject: [PATCH 096/116] virtiofsd: prevent races with lo_dirp_put() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Dr. David Alan Gilbert Message-id: <20200127190227.40942-93-dgilbert@redhat.com> Patchwork-id: 93546 O-Subject: [RHEL-AV-8.2 qemu-kvm PATCH 092/112] virtiofsd: prevent races with lo_dirp_put() Bugzilla: 1694164 RH-Acked-by: Philippe Mathieu-Daudé RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Sergio Lopez Pascual From: Stefan Hajnoczi Introduce lo_dirp_put() so that FUSE_RELEASEDIR does not cause use-after-free races with other threads that are accessing lo_dirp. Also make lo_releasedir() atomic to prevent FUSE_RELEASEDIR racing with itself. This prevents double-frees. Signed-off-by: Stefan Hajnoczi Reviewed-by: Philippe Mathieu-Daudé Signed-off-by: Dr. David Alan Gilbert (cherry picked from commit acefdde73b403576a241ebd8dbe8431ddc0d9442) Signed-off-by: Miroslav Rezanina --- tools/virtiofsd/passthrough_ll.c | 41 ++++++++++++++++++++++++++++++++++------ 1 file changed, 35 insertions(+), 6 deletions(-) diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c index 690edbc..2d703b5 100644 --- a/tools/virtiofsd/passthrough_ll.c +++ b/tools/virtiofsd/passthrough_ll.c @@ -1284,11 +1284,28 @@ static void lo_readlink(fuse_req_t req, fuse_ino_t ino) } struct lo_dirp { + gint refcount; DIR *dp; struct dirent *entry; off_t offset; }; +static void lo_dirp_put(struct lo_dirp **dp) +{ + struct lo_dirp *d = *dp; + + if (!d) { + return; + } + *dp = NULL; + + if (g_atomic_int_dec_and_test(&d->refcount)) { + closedir(d->dp); + free(d); + } +} + +/* Call lo_dirp_put() on the return value when no longer needed */ static struct lo_dirp *lo_dirp(fuse_req_t req, struct fuse_file_info *fi) { struct lo_data *lo = lo_data(req); @@ -1296,6 +1313,9 @@ static struct lo_dirp *lo_dirp(fuse_req_t req, struct fuse_file_info *fi) pthread_mutex_lock(&lo->mutex); elem = lo_map_get(&lo->dirp_map, fi->fh); + if (elem) { + g_atomic_int_inc(&elem->dirp->refcount); + } pthread_mutex_unlock(&lo->mutex); if (!elem) { return NULL; @@ -1331,6 +1351,7 @@ static void lo_opendir(fuse_req_t req, fuse_ino_t ino, d->offset = 0; d->entry = NULL; + g_atomic_int_set(&d->refcount, 1); /* paired with lo_releasedir() */ pthread_mutex_lock(&lo->mutex); fh = lo_add_dirp_mapping(req, d); pthread_mutex_unlock(&lo->mutex); @@ -1364,7 +1385,7 @@ static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size, off_t offset, struct fuse_file_info *fi, int plus) { struct lo_data *lo = lo_data(req); - struct lo_dirp *d; + struct lo_dirp *d = NULL; struct lo_inode *dinode; char *buf = NULL; char *p; @@ -1454,6 +1475,8 @@ static void lo_do_readdir(fuse_req_t req, fuse_ino_t ino, size_t size, err = 0; error: + lo_dirp_put(&d); + /* * If there's an error, we can only signal it if we haven't stored * any entries yet - otherwise we'd end up with wrong lookup @@ -1484,22 +1507,25 @@ static void lo_releasedir(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi) { struct lo_data *lo = lo_data(req); + struct lo_map_elem *elem; struct lo_dirp *d; (void)ino; - d = lo_dirp(req, fi); - if (!d) { + pthread_mutex_lock(&lo->mutex); + elem = lo_map_get(&lo->dirp_map, fi->fh); + if (!elem) { + pthread_mutex_unlock(&lo->mutex); fuse_reply_err(req, EBADF); return; } - pthread_mutex_lock(&lo->mutex); + d = elem->dirp; lo_map_remove(&lo->dirp_map, fi->fh); pthread_mutex_unlock(&lo->mutex); - closedir(d->dp); - free(d); + lo_dirp_put(&d); /* paired with lo_opendir() */ + fuse_reply_err(req, 0); } @@ -1710,6 +1736,9 @@ static void lo_fsyncdir(fuse_req_t req, fuse_ino_t ino, int datasync, } else { res = fsync(fd); } + + lo_dirp_put(&d); + fuse_reply_err(req, res == -1 ? errno : 0); } -- 1.8.3.1