Re: qcow2 api not secured by mutex lock

[Max Reitz]

On 19.12.19 11:02, Kevin Wolf wrote:
> Am 18.12.2019 um 11:28 hat Vladimir Sementsov-Ogievskiy geschrieben:

[...]

>> qcow2_write_snapshots actually called unlocked from
>> qcow2_check_fix_snapshot_table.. It seems unsafe.
> 
> This is curious, I'm not sure why you would drop the lock there. Max?
> 
> bdrv_flush() calls would have to replaced with qcow2_write_caches() to
> avoid a deadlock, but otherwise I don't see why we would want to drop
> the lock.
> 
> Of course, this should only be called from qemu-img check, so in
> practice it's probably not a bug.

Maybe I should have read all of this before replying...  Is
qcow2_write_caches() all that we want?  I mean, bdrv_flush() also
flushes the children (well, at least the file child right now).

OTOH qcow2_write_snapshots() probably does not need to take care of
actually flushing @bs, does it?

Max

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