[PATCH 3.18 31/52] block/loop: Use global lock for ioctl() operation.
From: Greg Kroah-Hartman
Date: Thu Jan 24 2019 - 14:24:07 EST
3.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx>
Reported-by: syzbot <syzbot+bf89c128e05dd6c62523@xxxxxxxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/block/loop.c | 47 ++++++++++++++++++++++++-----------------------
drivers/block/loop.h | 1 -
2 files changed, 24 insertions(+), 24 deletions(-)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -81,6 +81,7 @@
static DEFINE_IDR(loop_index_idr);
static DEFINE_MUTEX(loop_index_mutex);
+static DEFINE_MUTEX(loop_ctl_mutex);
static int max_part;
static int part_shift;
@@ -1012,7 +1013,7 @@ static int loop_clr_fd(struct loop_devic
*/
if (lo->lo_refcnt > 1) {
lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
return 0;
}
@@ -1061,12 +1062,12 @@ static int loop_clr_fd(struct loop_devic
lo->lo_flags = 0;
if (!part_shift)
lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
/*
- * Need not hold lo_ctl_mutex to fput backing file.
- * Calling fput holding lo_ctl_mutex triggers a circular
+ * Need not hold loop_ctl_mutex to fput backing file.
+ * Calling fput holding loop_ctl_mutex triggers a circular
* 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);
return 0;
@@ -1300,7 +1301,7 @@ static int lo_ioctl(struct block_device
struct loop_device *lo = bdev->bd_disk->private_data;
int err;
- mutex_lock_nested(&lo->lo_ctl_mutex, 1);
+ mutex_lock_nested(&loop_ctl_mutex, 1);
switch (cmd) {
case LOOP_SET_FD:
err = loop_set_fd(lo, mode, bdev, arg);
@@ -1309,7 +1310,7 @@ static int lo_ioctl(struct block_device
err = loop_change_fd(lo, bdev, arg);
break;
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);
if (!err)
goto out_unlocked;
@@ -1340,7 +1341,7 @@ static int lo_ioctl(struct block_device
default:
err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
}
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
out_unlocked:
return err;
@@ -1473,16 +1474,16 @@ static int lo_compat_ioctl(struct block_
switch(cmd) {
case LOOP_SET_STATUS:
- mutex_lock(&lo->lo_ctl_mutex);
+ mutex_lock(&loop_ctl_mutex);
err = loop_set_status_compat(
lo, (const struct compat_loop_info __user *) arg);
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
break;
case LOOP_GET_STATUS:
- mutex_lock(&lo->lo_ctl_mutex);
+ mutex_lock(&loop_ctl_mutex);
err = loop_get_status_compat(
lo, (struct compat_loop_info __user *) arg);
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
break;
case LOOP_SET_CAPACITY:
case LOOP_CLR_FD:
@@ -1513,9 +1514,9 @@ static int lo_open(struct block_device *
goto out;
}
- mutex_lock(&lo->lo_ctl_mutex);
+ mutex_lock(&loop_ctl_mutex);
lo->lo_refcnt++;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
out:
mutex_unlock(&loop_index_mutex);
return err;
@@ -1525,7 +1526,7 @@ static void __lo_release(struct loop_dev
{
int err;
- mutex_lock(&lo->lo_ctl_mutex);
+ mutex_lock(&loop_ctl_mutex);
if (--lo->lo_refcnt)
goto out;
@@ -1547,7 +1548,7 @@ static void __lo_release(struct loop_dev
}
out:
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
}
static void lo_release(struct gendisk *disk, fmode_t mode)
@@ -1593,10 +1594,10 @@ static int unregister_transfer_cb(int id
struct loop_device *lo = ptr;
struct loop_func_table *xfer = data;
- mutex_lock(&lo->lo_ctl_mutex);
+ mutex_lock(&loop_ctl_mutex);
if (lo->lo_encryption == xfer)
loop_release_xfer(lo);
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
return 0;
}
@@ -1677,7 +1678,7 @@ static int loop_add(struct loop_device *
if (!part_shift)
disk->flags |= GENHD_FL_NO_PART_SCAN;
disk->flags |= GENHD_FL_EXT_DEVT;
- mutex_init(&lo->lo_ctl_mutex);
+ mutex_init(&loop_ctl_mutex);
lo->lo_number = i;
lo->lo_thread = NULL;
init_waitqueue_head(&lo->lo_event);
@@ -1789,19 +1790,19 @@ static long loop_control_ioctl(struct fi
ret = loop_lookup(&lo, parm);
if (ret < 0)
break;
- mutex_lock(&lo->lo_ctl_mutex);
+ mutex_lock(&loop_ctl_mutex);
if (lo->lo_state != Lo_unbound) {
ret = -EBUSY;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
break;
}
if (lo->lo_refcnt > 0) {
ret = -EBUSY;
- mutex_unlock(&lo->lo_ctl_mutex);
+ mutex_unlock(&loop_ctl_mutex);
break;
}
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);
loop_remove(lo);
break;
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -55,7 +55,6 @@ struct loop_device {
struct bio_list lo_bio_list;
unsigned int lo_bio_count;
int lo_state;
- struct mutex lo_ctl_mutex;
struct task_struct *lo_thread;
wait_queue_head_t lo_event;
/* wait queue for incoming requests */