This is a note to let you know that I've just added the patch titled
xfrm: Don't disable preemption while looking up cache state.
to the 6.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xfrm-don-t-disable-preemption-while-looking-up-cache.patch
and it can be found in the queue-6.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 5fd029ebfc17e9ec1d3bfc415bdf0c51a17a63c8
Author: Sebastian Sewior <bigeasy@xxxxxxxxxxxxx>
Date: Thu Jan 23 17:20:45 2025 +0100
xfrm: Don't disable preemption while looking up cache state.
[ 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@xxxxxxxxx>
Closes: https://lore.kernel.org/all/CAADnVQKkCLaj=roayH=Mjiiqz_svdf1tsC3OE4EC0E=mAD+L1A@xxxxxxxxxxxxxx/
Fixes: 81a331a0e72dd ("xfrm: Add an inbound percpu state cache.")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 1781728ca4285..711e816fc4041 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);
