6.12-stable review patch. If anyone has any objections, please let me know.
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From: Sebastian Sewior bigeasy@linutronix.de
[ Upstream commit 6c9b7db96db62ee9ad8d359d90ff468d462518c4 ]
For the state cache lookup xfrm_input_state_lookup() first disables preemption, to remain on the CPU and then retrieves a per-CPU pointer. Within the preempt-disable section it also acquires netns_xfrm::xfrm_state_lock, a spinlock_t. This lock must not be acquired with explicit disabled preemption (such as by get_cpu()) because this lock becomes a sleeping lock on PREEMPT_RT.
To remain on the same CPU is just an optimisation for the CPU local lookup. The actual modification of the per-CPU variable happens with netns_xfrm::xfrm_state_lock acquired.
Remove get_cpu() and use the state_cache_input on the current CPU.
Reported-by: Alexei Starovoitov alexei.starovoitov@gmail.com Closes: https://lore.kernel.org/all/CAADnVQKkCLaj=roayH=Mjiiqz_svdf1tsC3OE4EC0E=mAD+... Fixes: 81a331a0e72dd ("xfrm: Add an inbound percpu state cache.") Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Signed-off-by: Steffen Klassert steffen.klassert@secunet.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/xfrm/xfrm_state.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index 567f02ff88597..6441e94233daa 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -1150,9 +1150,8 @@ struct xfrm_state *xfrm_input_state_lookup(struct net *net, u32 mark, struct xfrm_hash_state_ptrs state_ptrs; struct hlist_head *state_cache_input; struct xfrm_state *x = NULL; - int cpu = get_cpu();
- state_cache_input = per_cpu_ptr(net->xfrm.state_cache_input, cpu); + state_cache_input = raw_cpu_ptr(net->xfrm.state_cache_input);
rcu_read_lock(); hlist_for_each_entry_rcu(x, state_cache_input, state_cache_input) { @@ -1186,7 +1185,6 @@ struct xfrm_state *xfrm_input_state_lookup(struct net *net, u32 mark,
out: rcu_read_unlock(); - put_cpu(); return x; } EXPORT_SYMBOL(xfrm_input_state_lookup);