Thread (5 messages) 5 messages, 3 authors, 2021-10-26
STALE1716d
Revisions (2)
  1. v1 current
  2. v2 [diff vs current]

[PATCH bpf 2/2] bpf: fixes possible race in update_prog_stats() for 32bit arches

From: Eric Dumazet <hidden>
Date: 2021-10-26 20:38:40
Also in: bpf
Subsystem: bpf [core], bpf [general] (safe dynamic programs and tools), the rest · Maintainers: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds

From: Eric Dumazet <edumazet@google.com>

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>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
---
 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 fe1e857324e6683cecf5f88d24e0790f7ec72253..d3a307a8c42b95692f082f23f01e1ed470e63dec 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -585,11 +585,13 @@ 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);
 	}
 }
 
-- 
2.33.0.1079.g6e70778dc9-goog
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