[PATCH 6.1.y v2] io_uring/io-wq: Fix memory leak in io_wq_create() on success path

[Chen Xiaokun <shinnkka1@gmail.com>]

[ This is a stable-only patch for 6.1.y ]

Commit 657ca82526d0 ("io_uring/io-wq: inherit cpuset of cgroup in io
worker") was backported from upstream commit 84eacf177faa to 6.1.y.

In linux-6.1.y, this backport introduced a temporary allowed_mask 
variable in io_wq_create().  It is correctly freed on the error path,
but is not freed on the success path.  As a result, every successful
call to io_wq_create() leaks cpumask_size() bytes of memory.

This is a 6.1-specific backport issue caused by the differences in the
io-wq implementation, so the fix only applies to 6.1.y.

Fixes: 657ca82526d0 ("io_uring/io-wq: inherit cpuset of cgroup in io worker")
Signed-off-by: Chen Xiaokun <shinnkka1@gmail.com>

---
Hi Greg, Sasha, and io-uring maintainers,

This patch is specific to 6.1.y.  Commit 657ca82526d0 was a manual
backport of upstream commit 84eacf177faa ("io_uring/io-wq: inherit
cpuset of cgroup in io worker").  Due to significant differences in
the io-wq implementation between 6.1 and later kernels, the upstream
change had to be adapted for 6.1.

Later stable kernels do not contain this 6.1-specific backported
implementation of io_wq_create(), and therefore do not contain the
leaked allowed_mask.  The corresponding upstream implementation also
does not have this allocation.

Therefore, this fix is only applicable to 6.1.y and should not be
backported to other stable kernel series.

upstream patch: https://lore.kernel.org/all/20240910171157.166423-3-felix.moessbauer@siemens.com/
backport patch: https://lore.kernel.org/all/20240911162316.516725-3-felix.moessbauer@siemens.com/

Could you please queue it for 6.1.y?

Thanks,
Chen Xiaokun

Changes since v1:
- Reword the commit message (clarify that this is a 6.1-specific backport patch)
- No functional changes

 io_uring/io-wq.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index 0c3de2fead81..f1bc212309c8 100644
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -1221,6 +1221,7 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 	wq->task = get_task_struct(data->task);
 	atomic_set(&wq->worker_refs, 1);
 	init_completion(&wq->worker_done);
+	free_cpumask_var(allowed_mask);
 	return wq;
 err:
 	io_wq_put_hash(data->hash);
-- 
2.55.0