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block/loop: Use global lock for ioctl() operation.

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commit 310ca162d779efee8a2dc3731439680f3e9c1e86 upstream.

syzbot is reporting NULL pointer dereference [1] which is caused by
race condition between ioctl(loop_fd, LOOP_CLR_FD, 0) versus
ioctl(other_loop_fd, LOOP_SET_FD, loop_fd) due to traversing other
loop devices at loop_validate_file() without holding corresponding
lo->lo_ctl_mutex locks.

Since ioctl() request on loop devices is not frequent operation, we don't
need fine grained locking. Let's use global lock in order to allow safe
traversal at loop_validate_file().

Note that syzbot is also reporting circular locking dependency between
bdev->bd_mutex and lo->lo_ctl_mutex [2] which is caused by calling
blkdev_reread_part() with lock held. This patch does not address it.

[1] https://syzkaller.appspot.com/bug?id=f3cfe26e785d85f9ee259f385515291d21bd80a3
[2] https://syzkaller.appspot.com/bug?id=bf154052f0eea4bc7712499e4569505907d15889

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: syzbot <syzbot+bf89c128e05dd6c62523@syzkaller.appspotmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tetsuo Handa 2018-11-08 14:01:02 +01:00 committed by Greg Kroah-Hartman
parent f5d3c785c1
commit 342b3360ae
2 changed files with 29 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

58
drivers/block/loop.c
View File

@ -84,6 +84,7 @@
static DEFINE_IDR(loop_index_idr); static DEFINE_IDR(loop_index_idr);
static DEFINE_MUTEX(loop_index_mutex); static DEFINE_MUTEX(loop_index_mutex);
static DEFINE_MUTEX(loop_ctl_mutex);
static int max_part; static int max_part;
static int part_shift; static int part_shift;
@ -1047,7 +1048,7 @@ static int loop_clr_fd(struct loop_device *lo)
*/ */
if (atomic_read(&lo->lo_refcnt) > 1) { if (atomic_read(&lo->lo_refcnt) > 1) {
lo->lo_flags |= LO_FLAGS_AUTOCLEAR; lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
return 0; return 0;
} }
@ -1100,12 +1101,12 @@ static int loop_clr_fd(struct loop_device *lo)
if (!part_shift) if (!part_shift)
lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN; lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
loop_unprepare_queue(lo); loop_unprepare_queue(lo);
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
/* /*
* Need not hold lo_ctl_mutex to fput backing file. * Need not hold loop_ctl_mutex to fput backing file.
* Calling fput holding lo_ctl_mutex triggers a circular * Calling fput holding loop_ctl_mutex triggers a circular
* lock dependency possibility warning as fput can take * lock dependency possibility warning as fput can take
* bd_mutex which is usually taken before lo_ctl_mutex. * bd_mutex which is usually taken before loop_ctl_mutex.
*/ */
fput(filp); fput(filp);
return 0; return 0;
@ -1210,7 +1211,7 @@ loop_get_status(struct loop_device *lo, struct loop_info64 *info)
int ret; int ret;
if (lo->lo_state != Lo_bound) { if (lo->lo_state != Lo_bound) {
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
return -ENXIO; return -ENXIO;
} }
@ -1229,10 +1230,10 @@ loop_get_status(struct loop_device *lo, struct loop_info64 *info)
lo->lo_encrypt_key_size); lo->lo_encrypt_key_size);
} }
/* Drop lo_ctl_mutex while we call into the filesystem. */ /* Drop loop_ctl_mutex while we call into the filesystem. */
path = lo->lo_backing_file->f_path; path = lo->lo_backing_file->f_path;
path_get(&path); path_get(&path);
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
ret = vfs_getattr(&path, &stat, STATX_INO, AT_STATX_SYNC_AS_STAT); ret = vfs_getattr(&path, &stat, STATX_INO, AT_STATX_SYNC_AS_STAT);
if (!ret) { if (!ret) {
info->lo_device = huge_encode_dev(stat.dev); info->lo_device = huge_encode_dev(stat.dev);
@ -1324,7 +1325,7 @@ loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
int err; int err;
if (!arg) { if (!arg) {
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
return -EINVAL; return -EINVAL;
} }
err = loop_get_status(lo, &info64); err = loop_get_status(lo, &info64);
@ -1342,7 +1343,7 @@ loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
int err; int err;
if (!arg) { if (!arg) {
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
return -EINVAL; return -EINVAL;
} }
err = loop_get_status(lo, &info64); err = loop_get_status(lo, &info64);
@ -1400,7 +1401,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
struct loop_device *lo = bdev->bd_disk->private_data; struct loop_device *lo = bdev->bd_disk->private_data;
int err; int err;
err = mutex_lock_killable_nested(&lo->lo_ctl_mutex, 1); err = mutex_lock_killable_nested(&loop_ctl_mutex, 1);
if (err) if (err)
goto out_unlocked; goto out_unlocked;
@ -1412,7 +1413,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
err = loop_change_fd(lo, bdev, arg); err = loop_change_fd(lo, bdev, arg);
break; break;
case LOOP_CLR_FD: case LOOP_CLR_FD:
/* loop_clr_fd would have unlocked lo_ctl_mutex on success */ /* loop_clr_fd would have unlocked loop_ctl_mutex on success */
err = loop_clr_fd(lo); err = loop_clr_fd(lo);
if (!err) if (!err)
goto out_unlocked; goto out_unlocked;
@ -1425,7 +1426,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
break; break;
case LOOP_GET_STATUS: case LOOP_GET_STATUS:
err = loop_get_status_old(lo, (struct loop_info __user *) arg); err = loop_get_status_old(lo, (struct loop_info __user *) arg);
/* loop_get_status() unlocks lo_ctl_mutex */ /* loop_get_status() unlocks loop_ctl_mutex */
goto out_unlocked; goto out_unlocked;
case LOOP_SET_STATUS64: case LOOP_SET_STATUS64:
err = -EPERM; err = -EPERM;
@ -1435,7 +1436,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
break; break;
case LOOP_GET_STATUS64: case LOOP_GET_STATUS64:
err = loop_get_status64(lo, (struct loop_info64 __user *) arg); err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
/* loop_get_status() unlocks lo_ctl_mutex */ /* loop_get_status() unlocks loop_ctl_mutex */
goto out_unlocked; goto out_unlocked;
case LOOP_SET_CAPACITY: case LOOP_SET_CAPACITY:
err = -EPERM; err = -EPERM;
@ -1455,7 +1456,7 @@ static int lo_ioctl(struct block_device *bdev, fmode_t mode,
default: default:
err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL; err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
} }
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
out_unlocked: out_unlocked:
return err; return err;
@ -1572,7 +1573,7 @@ loop_get_status_compat(struct loop_device *lo,
int err; int err;
if (!arg) { if (!arg) {
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
return -EINVAL; return -EINVAL;
} }
err = loop_get_status(lo, &info64); err = loop_get_status(lo, &info64);
@ -1589,19 +1590,19 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
switch(cmd) { switch(cmd) {
case LOOP_SET_STATUS: case LOOP_SET_STATUS:
err = mutex_lock_killable(&lo->lo_ctl_mutex); err = mutex_lock_killable(&loop_ctl_mutex);
if (!err) { if (!err) {
err = loop_set_status_compat(lo, err = loop_set_status_compat(lo,
(const struct compat_loop_info __user *)arg); (const struct compat_loop_info __user *)arg);
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
} }
break; break;
case LOOP_GET_STATUS: case LOOP_GET_STATUS:
err = mutex_lock_killable(&lo->lo_ctl_mutex); err = mutex_lock_killable(&loop_ctl_mutex);
if (!err) { if (!err) {
err = loop_get_status_compat(lo, err = loop_get_status_compat(lo,
(struct compat_loop_info __user *)arg); (struct compat_loop_info __user *)arg);
/* loop_get_status() unlocks lo_ctl_mutex */ /* loop_get_status() unlocks loop_ctl_mutex */
} }
break; break;
case LOOP_SET_CAPACITY: case LOOP_SET_CAPACITY:
@ -1648,7 +1649,7 @@ static void __lo_release(struct loop_device *lo)
if (atomic_dec_return(&lo->lo_refcnt)) if (atomic_dec_return(&lo->lo_refcnt))
return; return;
mutex_lock(&lo->lo_ctl_mutex); mutex_lock(&loop_ctl_mutex);
if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) { if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
/* /*
* In autoclear mode, stop the loop thread * In autoclear mode, stop the loop thread
@ -1666,7 +1667,7 @@ static void __lo_release(struct loop_device *lo)
blk_mq_unfreeze_queue(lo->lo_queue); blk_mq_unfreeze_queue(lo->lo_queue);
} }
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
} }
static void lo_release(struct gendisk *disk, fmode_t mode) static void lo_release(struct gendisk *disk, fmode_t mode)
@ -1712,10 +1713,10 @@ static int unregister_transfer_cb(int id, void *ptr, void *data)
struct loop_device *lo = ptr; struct loop_device *lo = ptr;
struct loop_func_table *xfer = data; struct loop_func_table *xfer = data;
mutex_lock(&lo->lo_ctl_mutex); mutex_lock(&loop_ctl_mutex);
if (lo->lo_encryption == xfer) if (lo->lo_encryption == xfer)
loop_release_xfer(lo); loop_release_xfer(lo);
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
return 0; return 0;
} }
@ -1896,7 +1897,6 @@ static int loop_add(struct loop_device **l, int i)
if (!part_shift) if (!part_shift)
disk->flags |= GENHD_FL_NO_PART_SCAN; disk->flags |= GENHD_FL_NO_PART_SCAN;
disk->flags |= GENHD_FL_EXT_DEVT; disk->flags |= GENHD_FL_EXT_DEVT;
mutex_init(&lo->lo_ctl_mutex);
atomic_set(&lo->lo_refcnt, 0); atomic_set(&lo->lo_refcnt, 0);
lo->lo_number = i; lo->lo_number = i;
spin_lock_init(&lo->lo_lock); spin_lock_init(&lo->lo_lock);
@ -2009,21 +2009,21 @@ static long loop_control_ioctl(struct file *file, unsigned int cmd,
ret = loop_lookup(&lo, parm); ret = loop_lookup(&lo, parm);
if (ret < 0) if (ret < 0)
break; break;
ret = mutex_lock_killable(&lo->lo_ctl_mutex); ret = mutex_lock_killable(&loop_ctl_mutex);
if (ret) if (ret)
break; break;
if (lo->lo_state != Lo_unbound) { if (lo->lo_state != Lo_unbound) {
ret = -EBUSY; ret = -EBUSY;
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
break; break;
} }
if (atomic_read(&lo->lo_refcnt) > 0) { if (atomic_read(&lo->lo_refcnt) > 0) {
ret = -EBUSY; ret = -EBUSY;
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
break; break;
} }
lo->lo_disk->private_data = NULL; lo->lo_disk->private_data = NULL;
mutex_unlock(&lo->lo_ctl_mutex); mutex_unlock(&loop_ctl_mutex);
idr_remove(&loop_index_idr, lo->lo_number); idr_remove(&loop_index_idr, lo->lo_number);
loop_remove(lo); loop_remove(lo);
break; break;

1
drivers/block/loop.h
View File

@ -54,7 +54,6 @@ struct loop_device {
spinlock_t lo_lock; spinlock_t lo_lock;
int lo_state; int lo_state;
struct mutex lo_ctl_mutex;
struct kthread_worker worker; struct kthread_worker worker;
struct task_struct *worker_task; struct task_struct *worker_task;
bool use_dio; bool use_dio;