[0/2] Fix kobject error path memleaks

Message

Tobin C. Harding May 13, 2019, 3:39 a.m. UTC

Hi,

Is it ok to send patches during the merge window?  Applies on top of
Linus' mainline tag: v5.1, happy to rebase if there are conflicts.

While auditing kobject_init_and_add() calls throughout the kernel it was
found that btrfs potentially has a couple of memleaks in the error path
code for kobject_init_and_add().

Failing calls to kobject_init_and_add() should be followed by a call to
kobject_put() since kobject_init_and_add() always calls kobject_init().

Of note, adding kobject_put() causes the release method to be called if
kobject_init_and_add() fails.  For patch #1 this means we don't have to
manually free the space_info or call percpu_counter_destroy() since
these are both done by the release method.  In the second patch, I
believe the added call to kobject_put() fits in with the fs_devices
lifecycle assumptions of open_ctree() but please could you review since
I am new to this code.

CC'ing the kobject maintainers/reviewers also.

Thanks,
Tobin.


Tobin C. Harding (2):
  fs: btrfs: Fix error path kobject memory leak
  fs: btrfs: Don't leak memory when failing add fsid

 fs/btrfs/extent-tree.c | 3 +--
 fs/btrfs/sysfs.c       | 7 ++++++-
 2 files changed, 7 insertions(+), 3 deletions(-)

Comments

David Sterba May 13, 2019, 5:47 p.m. UTC | #1

On Mon, May 13, 2019 at 01:39:10PM +1000, Tobin C. Harding wrote:
> Is it ok to send patches during the merge window?

Yes (depends on subsystem), the feedback for patches that are not fixes
could be delayed after the merge window closes.

> Applies on top of
> Linus' mainline tag: v5.1, happy to rebase if there are conflicts.
> 
> While auditing kobject_init_and_add() calls throughout the kernel it was
> found that btrfs potentially has a couple of memleaks in the error path
> code for kobject_init_and_add().
> 
> Failing calls to kobject_init_and_add() should be followed by a call to
> kobject_put() since kobject_init_and_add() always calls kobject_init().
> 
> Of note, adding kobject_put() causes the release method to be called if
> kobject_init_and_add() fails.  For patch #1 this means we don't have to
> manually free the space_info or call percpu_counter_destroy() since
> these are both done by the release method.  In the second patch, I
> believe the added call to kobject_put() fits in with the fs_devices
> lifecycle assumptions of open_ctree() but please could you review since
> I am new to this code.

We use the cleanup-after-error pattern where it's up to the callee to
clean up, so it's right to do it like as you did. Patches added to the
queue that's for 5.2-rcX. Thanks.