Re: [PATCH for-rc 1/2] IB/hfi1: Fix memory leaks in sysfs registration and unregistration

[Jason Gunthorpe <jgg@ziepe.ca>]

On Thu, Mar 26, 2020 at 12:38:07PM -0400, Dennis Dalessandro wrote:
> From: Kaike Wan <kaike.wan@intel.com>
> 
> When the hfi1 driver is unloaded, kmemleak will report the following
> issue:
> 
> unreferenced object 0xffff8888461a4c08 (size 8):
> comm "kworker/0:0", pid 5, jiffies 4298601264 (age 2047.134s)
> hex dump (first 8 bytes):
> 73 64 6d 61 30 00 ff ff sdma0...
> backtrace:
> [<00000000311a6ef5>] kvasprintf+0x62/0xd0
> [<00000000ade94d9f>] kobject_set_name_vargs+0x1c/0x90
> [<0000000060657dbb>] kobject_init_and_add+0x5d/0xb0
> [<00000000346fe72b>] 0xffffffffa0c5ecba
> [<000000006cfc5819>] 0xffffffffa0c866b9
> [<0000000031c65580>] 0xffffffffa0c38e87
> [<00000000e9739b3f>] local_pci_probe+0x41/0x80
> [<000000006c69911d>] work_for_cpu_fn+0x16/0x20
> [<00000000601267b5>] process_one_work+0x171/0x380
> [<0000000049a0eefa>] worker_thread+0x1d1/0x3f0
> [<00000000909cf2b9>] kthread+0xf8/0x130
> [<0000000058f5f874>] ret_from_fork+0x35/0x40
> 
> This patch fixes the issue by:
> - Releasing dd->per_sdma[i].kobject in hfi1_unregister_sysfs().
>   - This will fix the memory leak.
> - Calling kobject_put() to unwind operations only for those entries in
>    dd->per_sdma[] whose operations have succeeded (including the current
>    one that has just failed) in hfi1_verbs_register_sysfs().
> 
> Fixes: 0cb2aa690c7e ("IB/hfi1: Add sysfs interface for affinity setup")
> Cc: <stable@vger.kernel.org>
> Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
> Signed-off-by: Kaike Wan <kaike.wan@intel.com>
> Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
> ---
>  drivers/infiniband/hw/hfi1/sysfs.c |   13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)

I'm not certain, but this seems unwise.

After hfi1_verbs_unregiser_sysfs() returns there should be no sysfs left
under the ibdev as we are going to delete the ibdev sysfs next.

kobject_del() triggers synchronous delete of the sysfs, while
kobject_put() potentially defers it to the future.

Will ib unregister fail if the kobject_del() has not happened yet? I
am unsure.

Jason