* [bpf-next] bpf: Fix possible race in inc_misses_counter
@ 2022-01-22 10:29 He Fengqing
2022-01-25 19:55 ` John Fastabend
0 siblings, 1 reply; 2+ messages in thread
From: He Fengqing @ 2022-01-22 10:29 UTC (permalink / raw)
To: ast, daniel, andrii, kafai
Cc: songliubraving, yhs, john.fastabend, kpsingh, netdev, bpf, linux-kernel
It seems inc_misses_counter() suffers from same issue fixed in
the commit d979617aa84d ("bpf: Fixes possible race in update_prog_stats()
for 32bit arches"):
As it can run while interrupts are enabled, it could
be re-entered and the u64_stats syncp could be mangled.
Fixes: 9ed9e9ba2337 ("bpf: Count the number of times recursion was prevented")
Signed-off-by: He Fengqing <hefengqing@huawei.com>
---
kernel/bpf/trampoline.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index 4b6974a195c1..5e7edf913060 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -550,11 +550,12 @@ static __always_inline u64 notrace bpf_prog_start_time(void)
static void notrace inc_misses_counter(struct bpf_prog *prog)
{
struct bpf_prog_stats *stats;
+ unsigned int flags;
stats = this_cpu_ptr(prog->stats);
- u64_stats_update_begin(&stats->syncp);
+ flags = u64_stats_update_begin_irqsave(&stats->syncp);
u64_stats_inc(&stats->misses);
- u64_stats_update_end(&stats->syncp);
+ u64_stats_update_end_irqrestore(&stats->syncp, flags);
}
/* The logic is similar to bpf_prog_run(), but with an explicit
--
2.25.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* RE: [bpf-next] bpf: Fix possible race in inc_misses_counter
2022-01-22 10:29 [bpf-next] bpf: Fix possible race in inc_misses_counter He Fengqing
@ 2022-01-25 19:55 ` John Fastabend
0 siblings, 0 replies; 2+ messages in thread
From: John Fastabend @ 2022-01-25 19:55 UTC (permalink / raw)
To: He Fengqing, ast, daniel, andrii, kafai
Cc: songliubraving, yhs, john.fastabend, kpsingh, netdev, bpf, linux-kernel
He Fengqing wrote:
> It seems inc_misses_counter() suffers from same issue fixed in
> the commit d979617aa84d ("bpf: Fixes possible race in update_prog_stats()
> for 32bit arches"):
> As it can run while interrupts are enabled, it could
> be re-entered and the u64_stats syncp could be mangled.
>
> Fixes: 9ed9e9ba2337 ("bpf: Count the number of times recursion was prevented")
> Signed-off-by: He Fengqing <hefengqing@huawei.com>
> ---
> kernel/bpf/trampoline.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
Appears possible through sleepable progs.
Acked-by: John Fastabend <john.fastabend@gmail.com>
> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index 4b6974a195c1..5e7edf913060 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
> @@ -550,11 +550,12 @@ static __always_inline u64 notrace bpf_prog_start_time(void)
> static void notrace inc_misses_counter(struct bpf_prog *prog)
> {
> struct bpf_prog_stats *stats;
> + unsigned int flags;
>
> stats = this_cpu_ptr(prog->stats);
> - u64_stats_update_begin(&stats->syncp);
> + flags = u64_stats_update_begin_irqsave(&stats->syncp);
> u64_stats_inc(&stats->misses);
> - u64_stats_update_end(&stats->syncp);
> + u64_stats_update_end_irqrestore(&stats->syncp, flags);
> }
>
> /* The logic is similar to bpf_prog_run(), but with an explicit
> --
> 2.25.1
>
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