diff mbox series

[bpf-next,v2,2/4] bpf: Use this_cpu_{inc_return|dec} for prog->active

Message ID 20220901061938.3789460-3-houtao@huaweicloud.com (mailing list archive)
State Accepted
Commit c89e843a11f1075d27684f6b42256213e4592383
Delegated to: BPF
Headers show
Series Use this_cpu_xxx for preemption-safety | expand

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netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 2 this patch: 2
netdev/cc_maintainers warning 2 maintainers not CCed: song@kernel.org martin.lau@linux.dev
netdev/build_clang success Errors and warnings before: 5 this patch: 5
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netdev/build_allmodconfig_warn success Errors and warnings before: 2 this patch: 2
netdev/checkpatch warning CHECK: Unnecessary parentheses around 'prog->active' CHECK: Unnecessary parentheses around prog->active
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Commit Message

Hou Tao Sept. 1, 2022, 6:19 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

Both __this_cpu_inc_return() and __this_cpu_dec() are not preemption
safe and now migrate_disable() doesn't disable preemption, so the update
of prog-active is not atomic and in theory under fully preemptible kernel
recurisve prevention may do not work.

Fixing by using the preemption-safe and IRQ-safe variants.

Fixes: ca06f55b9002 ("bpf: Add per-program recursion prevention mechanism")
Signed-off-by: Hou Tao <houtao1@huawei.com>
---
 kernel/bpf/trampoline.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
index ff87e38af8a7..ad76940b02cc 100644
--- a/kernel/bpf/trampoline.c
+++ b/kernel/bpf/trampoline.c
@@ -895,7 +895,7 @@  u64 notrace __bpf_prog_enter(struct bpf_prog *prog, struct bpf_tramp_run_ctx *ru
 
 	run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx);
 
-	if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
+	if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
 		inc_misses_counter(prog);
 		return 0;
 	}
@@ -930,7 +930,7 @@  void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start, struct bpf_tramp_
 	bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 
 	update_prog_stats(prog, start);
-	__this_cpu_dec(*(prog->active));
+	this_cpu_dec(*(prog->active));
 	migrate_enable();
 	rcu_read_unlock();
 }
@@ -966,7 +966,7 @@  u64 notrace __bpf_prog_enter_sleepable(struct bpf_prog *prog, struct bpf_tramp_r
 	migrate_disable();
 	might_fault();
 
-	if (unlikely(__this_cpu_inc_return(*(prog->active)) != 1)) {
+	if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) {
 		inc_misses_counter(prog);
 		return 0;
 	}
@@ -982,7 +982,7 @@  void notrace __bpf_prog_exit_sleepable(struct bpf_prog *prog, u64 start,
 	bpf_reset_run_ctx(run_ctx->saved_run_ctx);
 
 	update_prog_stats(prog, start);
-	__this_cpu_dec(*(prog->active));
+	this_cpu_dec(*(prog->active));
 	migrate_enable();
 	rcu_read_unlock_trace();
 }