[PATCH 5.14 524/849] bpf: Fixes possible race in update_prog_stats() for 32bit arches

Greg Kroah-Hartman
2021-11-16T01:24:04Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit d979617aa84d96acca44c2f5778892b4565e322f ]

It seems update_prog_stats() suffers from same issue fixed
in the prior patch:

As it can run while interrupts are enabled, it could
be re-entered and the u64_stats syncp could be mangled.

Fixes: fec56f5890d9 ("bpf: Introduce BPF trampoline")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211026214133.3114279-3-eric.dumazet@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/trampoline.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 28a3630c48ee1..9587e5ebddaa3 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -579,11 +579,13 @@ static void notrace update_prog_stats(struct bpf_prog *prog,
* Hence check that 'start' is valid.
*/
start > NO_START_TIME) {
+ unsigned long flags;
+
stats = this_cpu_ptr(prog->stats);
- u64_stats_update_begin(&stats->syncp);
+ flags = u64_stats_update_begin_irqsave(&stats->syncp);
stats->cnt++;
stats->nsecs += sched_clock() - start;
- u64_stats_update_end(&stats->syncp);
+ u64_stats_update_end_irqrestore(&stats->syncp, flags);
}
}

--
2.33.0