Do not call loop_unplug for not configured loop device.
In loop_unplug() function is expected that mapping is set
and lo->lo_backing_file is not NULL.
Unfortunately loop_set_fd() set the request queue unplug function,
but loop_clr_fd() doesn't clear that.
Loop device allows open of non-configured loop in some situations.
If the unplug on request queue is called, loop module oopses because
of missing lo_backing_file.
Simple reproducer:
losetup /dev/loop0 /xxx
losetup -d /dev/loop0
dmsetup create x --table "0 1 linear /dev/loop0 0"
EIP is at loop_unplug+0x1d/0x3b
...
Call Trace:
blk_unplug+0x57/0x5e
dm_table_unplug_all+0x34/0x77 [dm_mod]
destroy_inode+0x27/0x38
generic_delete_inode+0xd5/0xd9
iput+0x4b/0x4e
dm_resume+0xca/0xfe [dm_mod]
dev_suspend+0x143/0x165 [dm_mod]
dm_ctl_ioctl+0x18e/0x1cf [dm_mod]
dev_suspend+0x0/0x165 [dm_mod]
dm_ctl_ioctl+0x0/0x1cf [dm_mod]
vfs_ioctl+0x22/0x69
do_vfs_ioctl+0x39d/0x3c7
trace_hardirqs_on+0xb/0xd
remove_vma+0x50/0x56
do_munmap+0x21c/0x237
sys_ioctl+0x2c/0x45
sysenter_do_call+0x12/0x31
Several reports here
http://www.kerneloops.org/search.php?search=loop_unplug
Fix it by simply clear unplug function together with
removing of backing file.
Signed-off-by: Milan Broz <[email protected]>
---
drivers/block/loop.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 90d19df..1e4b41e 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -919,6 +919,7 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
kthread_stop(lo->lo_thread);
+ lo->lo_queue->unplug_fn = NULL;
lo->lo_backing_file = NULL;
loop_release_xfer(lo);
On Fri, Dec 12 2008, Milan Broz wrote:
> Do not call loop_unplug for not configured loop device.
>
> In loop_unplug() function is expected that mapping is set
> and lo->lo_backing_file is not NULL.
>
> Unfortunately loop_set_fd() set the request queue unplug function,
> but loop_clr_fd() doesn't clear that.
>
> Loop device allows open of non-configured loop in some situations.
> If the unplug on request queue is called, loop module oopses because
> of missing lo_backing_file.
>
> Simple reproducer:
> losetup /dev/loop0 /xxx
> losetup -d /dev/loop0
> dmsetup create x --table "0 1 linear /dev/loop0 0"
>
> EIP is at loop_unplug+0x1d/0x3b
> ...
> Call Trace:
> blk_unplug+0x57/0x5e
> dm_table_unplug_all+0x34/0x77 [dm_mod]
> destroy_inode+0x27/0x38
> generic_delete_inode+0xd5/0xd9
> iput+0x4b/0x4e
> dm_resume+0xca/0xfe [dm_mod]
> dev_suspend+0x143/0x165 [dm_mod]
> dm_ctl_ioctl+0x18e/0x1cf [dm_mod]
> dev_suspend+0x0/0x165 [dm_mod]
> dm_ctl_ioctl+0x0/0x1cf [dm_mod]
> vfs_ioctl+0x22/0x69
> do_vfs_ioctl+0x39d/0x3c7
> trace_hardirqs_on+0xb/0xd
> remove_vma+0x50/0x56
> do_munmap+0x21c/0x237
> sys_ioctl+0x2c/0x45
> sysenter_do_call+0x12/0x31
>
> Several reports here
> http://www.kerneloops.org/search.php?search=loop_unplug
>
> Fix it by simply clear unplug function together with
> removing of backing file.
>
> Signed-off-by: Milan Broz <[email protected]>
> ---
> drivers/block/loop.c | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 90d19df..1e4b41e 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -919,6 +919,7 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
>
> kthread_stop(lo->lo_thread);
>
> + lo->lo_queue->unplug_fn = NULL;
> lo->lo_backing_file = NULL;
>
> loop_release_xfer(lo);
>
>
Thanks, applied.
--
Jens Axboe