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| author | Thomas Gleixner <tglx@linutronix.de> | 2020-02-24 15:01:39 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-10-01 13:14:34 +0200 |
| commit | 1baf236084a366789eaf9515ee6027b515fb059d (patch) | |
| tree | 9211e60cea93d39ac0048b56a8f1ca2ce4d3202d | |
| parent | 03dda9566772f5a37c5053c6b6eaa184bb4e387d (diff) | |
| download | linux-stable-1baf236084a366789eaf9515ee6027b515fb059d.tar.gz linux-stable-1baf236084a366789eaf9515ee6027b515fb059d.tar.bz2 linux-stable-1baf236084a366789eaf9515ee6027b515fb059d.zip | |
bpf: Remove recursion prevention from rcu free callback
[ Upstream commit 8a37963c7ac9ecb7f86f8ebda020e3f8d6d7b8a0 ]
If an element is freed via RCU then recursion into BPF instrumentation
functions is not a concern. The element is already detached from the map
and the RCU callback does not hold any locks on which a kprobe, perf event
or tracepoint attached BPF program could deadlock.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200224145643.259118710@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | kernel/bpf/hashtab.c | 8 |
1 files changed, 0 insertions, 8 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 1b28fb006763..3f3ed33bd2fd 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -667,15 +667,7 @@ static void htab_elem_free_rcu(struct rcu_head *head) struct htab_elem *l = container_of(head, struct htab_elem, rcu); struct bpf_htab *htab = l->htab; - /* must increment bpf_prog_active to avoid kprobe+bpf triggering while - * we're calling kfree, otherwise deadlock is possible if kprobes - * are placed somewhere inside of slub - */ - preempt_disable(); - __this_cpu_inc(bpf_prog_active); htab_elem_free(htab, l); - __this_cpu_dec(bpf_prog_active); - preempt_enable(); } static void htab_put_fd_value(struct bpf_htab *htab, struct htab_elem *l) |