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authorDavid Sterba <dsterba@suse.com>2018-06-19 18:04:07 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-09-15 09:46:57 +0200
commit760d0077abc1d7730639767e712908c12f511741 (patch)
tree62aa8e1659740b71b66f1bee8d4dde74bc4c88ab /fs
parent49db06e7f366c26a71dd3589617b43c3110be649 (diff)
btrfs: fix mount and ioctl device scan ioctl race
[ Upstream commit 81ffd56b5745355b70d54ca4e1bdd0d64a66ff9f ] Technically this extends the critical section covered by uuid_mutex to: - parse early mount options -- here we can call device scan on paths that can be passed as 'device=/dev/...' - scan the device passed to mount - open the devices related to the fs_devices -- this increases fs_devices::opened The race can happen when mount calls one of the scans and there's another one called eg. by mkfs or 'btrfs dev scan': Mount Scan ----- ---- scan_one_device (dev1, fsid1) scan_one_device (dev2, fsid1) add the device free stale devices fsid1 fs_devices::opened == 0 find fsid1:dev1 free fsid1:dev1 if it's the last one, free fs_devices of fsid1 too open_devices (dev1, fsid1) dev1 not found When fixed, the uuid mutex will make sure that mount will increase fs_devices::opened and this will not be touched by the racing scan ioctl. Reported-and-tested-by: syzbot+909a5177749d7990ffa4@syzkaller.appspotmail.com Reported-and-tested-by: syzbot+ceb2606025ec1cc3479c@syzkaller.appspotmail.com Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: David Sterba <dsterba@suse.com> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/super.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index a8f2950b9200..9b25f29d0e73 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1557,19 +1557,19 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
mutex_lock(&uuid_mutex);
error = btrfs_parse_early_options(data, mode, fs_type, &fs_devices);
- mutex_unlock(&uuid_mutex);
- if (error)
+ if (error) {
+ mutex_unlock(&uuid_mutex);
goto error_fs_info;
+ }
- mutex_lock(&uuid_mutex);
error = btrfs_scan_one_device(device_name, mode, fs_type, &fs_devices);
- mutex_unlock(&uuid_mutex);
- if (error)
+ if (error) {
+ mutex_unlock(&uuid_mutex);
goto error_fs_info;
+ }
fs_info->fs_devices = fs_devices;
- mutex_lock(&uuid_mutex);
error = btrfs_open_devices(fs_devices, mode, fs_type);
mutex_unlock(&uuid_mutex);
if (error)