Re: [PATCH] RDMA/cm: Fix leaking the multicast GID table reference

[Jason Gunthorpe <jgg@nvidia.com>]

On Fri, Nov 28, 2025 at 08:53:21PM -0400, Jason Gunthorpe wrote:
> If the CM ID is destroyed while the CM event for multicast creating is
> still queued the cancel_work_sync() will prevent the work from running
> which also prevents destroying the ah_attr. This leaks a refcount and
> triggers a WARN:
> 
>    GID entry ref leak for dev syz1 index 2 ref=573
>    WARNING: CPU: 1 PID: 655 at drivers/infiniband/core/cache.c:809 release_gid_table drivers/infiniband/core/cache.c:806 [inline]
>    WARNING: CPU: 1 PID: 655 at drivers/infiniband/core/cache.c:809 gid_table_release_one+0x284/0x3cc drivers/infiniband/core/cache.c:886
> 
> Destroy the ah_attr after canceling the work, it is safe to call this
> twice.
> 
> Cc: stable@vger.kernel.org
> Fixes: fe454dc31e84 ("RDMA/ucma: Fix use-after-free bug in ucma_create_uevent")
> Reported-by: syzbot+b0da83a6c0e2e2bddbd4@syzkaller.appspotmail.com
> Closes: https://lore.kernel.org/all/68232e7b.050a0220.f2294.09f6.GAE@google.com
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/infiniband/core/cma.c | 2 ++
>  1 file changed, 2 insertions(+)

Applied to for-rc with the missing hunk

Jason