From: Al Viro viro@zeniv.linux.org.uk
[ Upstream commit a91714312eb16f9ecd1f7f8b3efe1380075f28d4 ]
That way percpu_ref_exit() is safe after failing percpu_ref_init(). At least one user (cgroup_create()) had a double-free that way; there might be other similar bugs. Easier to fix in percpu_ref_init(), rather than playing whack-a-mole in sloppy users...
Usual symptoms look like a messed refcounting in one of subsystems that use percpu allocations (might be percpu-refcount, might be something else). Having refcounts for two different objects share memory is Not Nice(tm)...
Reported-by: syzbot+5b1e53987f858500ec00@syzkaller.appspotmail.com Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- lib/percpu-refcount.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index e59eda07305e..493093b97093 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -75,6 +75,7 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release, data = kzalloc(sizeof(*ref->data), gfp); if (!data) { free_percpu((void __percpu *)ref->percpu_count_ptr); + ref->percpu_count_ptr = 0; return -ENOMEM; }