From: Greg Kurz <groug@kaod.org> To: Miklos Szeredi <miklos@szeredi.hu> Cc: linux-kernel@vger.kernel.org, Max Reitz <mreitz@redhat.com>, linux-fsdevel@vger.kernel.org, virtio-fs@redhat.com, Vivek Goyal <vgoyal@redhat.com>, Greg Kurz <groug@kaod.org> Subject: [PATCH v2 2/7] fuse: Fix crash if superblock of submount gets killed early Date: Fri, 4 Jun 2021 18:11:51 +0200 [thread overview] Message-ID: <20210604161156.408496-3-groug@kaod.org> (raw) In-Reply-To: <20210604161156.408496-1-groug@kaod.org> As soon as fuse_dentry_automount() does up_write(&sb->s_umount), the superblock can theoretically be killed. If this happens before the submount was added to the &fc->mounts list, fuse_mount_remove() later crashes in list_del_init() because it assumes the submount to be already there. Add the submount before dropping sb->s_umount to fix the inconsistency. It is okay to nest fc->killsb under sb->s_umount, we already do this on the ->kill_sb() path. Signed-off-by: Greg Kurz <groug@kaod.org> --- fs/fuse/dir.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 01559061cbfb..3fd1b71e546b 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -346,15 +346,15 @@ static struct vfsmount *fuse_dentry_automount(struct path *path) goto out_put_sb; } + down_write(&fc->killsb); + list_add_tail(&fm->fc_entry, &fc->mounts); + up_write(&fc->killsb); + sb->s_flags |= SB_ACTIVE; fsc->root = dget(sb->s_root); /* We are done configuring the superblock, so unlock it */ up_write(&sb->s_umount); - down_write(&fc->killsb); - list_add_tail(&fm->fc_entry, &fc->mounts); - up_write(&fc->killsb); - /* Create the submount */ mnt = vfs_create_mount(fsc); if (IS_ERR(mnt)) { -- 2.31.1
WARNING: multiple messages have this Message-ID (diff)
From: Greg Kurz <groug@kaod.org> To: Miklos Szeredi <miklos@szeredi.hu> Cc: linux-kernel@vger.kernel.org, virtio-fs@redhat.com, linux-fsdevel@vger.kernel.org, Max Reitz <mreitz@redhat.com>, Vivek Goyal <vgoyal@redhat.com> Subject: [Virtio-fs] [PATCH v2 2/7] fuse: Fix crash if superblock of submount gets killed early Date: Fri, 4 Jun 2021 18:11:51 +0200 [thread overview] Message-ID: <20210604161156.408496-3-groug@kaod.org> (raw) In-Reply-To: <20210604161156.408496-1-groug@kaod.org> As soon as fuse_dentry_automount() does up_write(&sb->s_umount), the superblock can theoretically be killed. If this happens before the submount was added to the &fc->mounts list, fuse_mount_remove() later crashes in list_del_init() because it assumes the submount to be already there. Add the submount before dropping sb->s_umount to fix the inconsistency. It is okay to nest fc->killsb under sb->s_umount, we already do this on the ->kill_sb() path. Signed-off-by: Greg Kurz <groug@kaod.org> --- fs/fuse/dir.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 01559061cbfb..3fd1b71e546b 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -346,15 +346,15 @@ static struct vfsmount *fuse_dentry_automount(struct path *path) goto out_put_sb; } + down_write(&fc->killsb); + list_add_tail(&fm->fc_entry, &fc->mounts); + up_write(&fc->killsb); + sb->s_flags |= SB_ACTIVE; fsc->root = dget(sb->s_root); /* We are done configuring the superblock, so unlock it */ up_write(&sb->s_umount); - down_write(&fc->killsb); - list_add_tail(&fm->fc_entry, &fc->mounts); - up_write(&fc->killsb); - /* Create the submount */ mnt = vfs_create_mount(fsc); if (IS_ERR(mnt)) { -- 2.31.1
next prev parent reply other threads:[~2021-06-04 16:12 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-04 16:11 [PATCH v2 0/7] fuse: Some fixes for submounts Greg Kurz 2021-06-04 16:11 ` [Virtio-fs] " Greg Kurz 2021-06-04 16:11 ` [PATCH v2 1/7] fuse: Fix crash in fuse_dentry_automount() error path Greg Kurz 2021-06-04 16:11 ` [Virtio-fs] " Greg Kurz 2021-06-04 16:11 ` Greg Kurz [this message] 2021-06-04 16:11 ` [Virtio-fs] [PATCH v2 2/7] fuse: Fix crash if superblock of submount gets killed early Greg Kurz 2021-06-08 15:08 ` Max Reitz 2021-06-08 15:08 ` [Virtio-fs] " Max Reitz 2021-06-04 16:11 ` [PATCH v2 3/7] fuse: Fix infinite loop in sget_fc() Greg Kurz 2021-06-04 16:11 ` [Virtio-fs] " Greg Kurz 2021-06-08 15:12 ` Max Reitz 2021-06-08 15:12 ` [Virtio-fs] " Max Reitz 2021-06-04 16:11 ` [PATCH v2 4/7] fuse: Add dedicated filesystem context ops for submounts Greg Kurz 2021-06-04 16:11 ` [Virtio-fs] " Greg Kurz 2021-06-08 15:25 ` Max Reitz 2021-06-08 15:25 ` [Virtio-fs] " Max Reitz 2021-06-04 16:11 ` [PATCH v2 5/7] fuse: Call vfs_get_tree() " Greg Kurz 2021-06-04 16:11 ` [Virtio-fs] " Greg Kurz 2021-06-08 15:40 ` Max Reitz 2021-06-08 15:40 ` [Virtio-fs] " Max Reitz 2021-06-04 16:11 ` [PATCH v2 6/7] fuse: Switch to fc_mount() " Greg Kurz 2021-06-04 16:11 ` [Virtio-fs] " Greg Kurz 2021-06-08 15:51 ` Max Reitz 2021-06-08 15:51 ` [Virtio-fs] " Max Reitz 2021-06-09 7:45 ` Greg Kurz 2021-06-09 7:45 ` [Virtio-fs] " Greg Kurz 2021-06-11 14:44 ` Miklos Szeredi 2021-06-11 14:44 ` [Virtio-fs] " Miklos Szeredi 2021-06-04 16:11 ` [PATCH v2 7/7] fuse: Make fuse_fill_super_submount() static Greg Kurz 2021-06-04 16:11 ` [Virtio-fs] " Greg Kurz 2021-06-08 15:52 ` [PATCH v2 0/7] fuse: Some fixes for submounts Max Reitz 2021-06-08 15:52 ` [Virtio-fs] " Max Reitz 2021-06-09 7:46 ` Greg Kurz 2021-06-09 7:46 ` [Virtio-fs] " Greg Kurz
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