On Wed, Feb 17, 2021 at 09:04:34AM +0300, Dan Carpenter wrote:

The problem is we're copying "inherit" from user space but we don't
necessarily know that we're copying enough data for a 64 byte
struct.  Then the next problem is that "inherit" has a variable size
array at the end, and we have to verify that array is the size we
expected.

Fixes: 6f72c7e20dba: ("Btrfs: add qgroup inheritance")
Signed-off-by: Dan Carpenter <redacted>
---
Presumably only root can create snapshots.

Well, no. After first analysis there are some "interesting memory access
patterns" possible, with a crafted data in the inherit member.

Anyway, I have not tested
this fix.  I believe it is correct, of course.  But perhaps it's best
to check.

Yeah I'll write a test also to see where exactly the issues are. Thanks
for the report/fix.