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percpu_ref: don't refer to ref->data if it isn't allocated

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We can't check ref->data->confirm_switch directly in __percpu_ref_exit(), since
ref->data may not be allocated in one not-initialized refcount.

Fixes: 2b0d3d3e4f ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
Reported-by: syzbot+fd15ff734dace9e16437@syzkaller.appspotmail.com
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2020-10-09 12:03:56 +08:00 committed by Jens Axboe
parent f4ac712e4f
commit 7ea6bf2e6c
1 changed files with 1 additions and 1 deletions
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2
lib/percpu-refcount.c
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@ -109,7 +109,7 @@ static void __percpu_ref_exit(struct percpu_ref *ref)
if (percpu_count) { if (percpu_count) {
/* non-NULL confirm_switch indicates switching in progress */ /* non-NULL confirm_switch indicates switching in progress */
WARN_ON_ONCE(ref->data->confirm_switch); WARN_ON_ONCE(ref->data && ref->data->confirm_switch);
free_percpu(percpu_count); free_percpu(percpu_count);
ref->percpu_count_ptr = __PERCPU_REF_ATOMIC_DEAD; ref->percpu_count_ptr = __PERCPU_REF_ATOMIC_DEAD;
} }