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| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2023-08-30 10:04:05 +0200 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2023-09-06 10:44:28 +0200 |
| commit | 6764e767f4af1e35f87f3497e1182d945de37f93 (patch) | |
| tree | 74f0a19f08a3904a3d898136382416fcfbee0f7d /kernel | |
| parent | 7645629f7dc88cd777f98970134bf1a54c8d77e3 (diff) | |
| download | linux-6764e767f4af1e35f87f3497e1182d945de37f93.tar.gz linux-6764e767f4af1e35f87f3497e1182d945de37f93.tar.bz2 linux-6764e767f4af1e35f87f3497e1182d945de37f93.zip | |
bpf: Assign bpf_tramp_run_ctx::saved_run_ctx before recursion check.
__bpf_prog_enter_recur() assigns bpf_tramp_run_ctx::saved_run_ctx before
performing the recursion check which means in case of a recursion
__bpf_prog_exit_recur() uses the previously set bpf_tramp_run_ctx::saved_run_ctx
value.
__bpf_prog_enter_sleepable_recur() assigns bpf_tramp_run_ctx::saved_run_ctx
after the recursion check which means in case of a recursion
__bpf_prog_exit_sleepable_recur() uses an uninitialized value. This does not
look right. If I read the entry trampoline code right, then bpf_tramp_run_ctx
isn't initialized upfront.
Align __bpf_prog_enter_sleepable_recur() with __bpf_prog_enter_recur() and
set bpf_tramp_run_ctx::saved_run_ctx before the recursion check is made.
Remove the assignment of saved_run_ctx in kern_sys_bpf() since it happens
a few cycles later.
Fixes: e384c7b7b46d0 ("bpf, x86: Create bpf_tramp_run_ctx on the caller thread's stack")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20230830080405.251926-3-bigeasy@linutronix.de
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/syscall.c | 1 | ||||
| -rw-r--r-- | kernel/bpf/trampoline.c | 5 |
2 files changed, 2 insertions, 4 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 53a0b62464e9..eb01c31ed591 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -5502,7 +5502,6 @@ int kern_sys_bpf(int cmd, union bpf_attr *attr, unsigned int size) } run_ctx.bpf_cookie = 0; - run_ctx.saved_run_ctx = NULL; if (!__bpf_prog_enter_sleepable_recur(prog, &run_ctx)) { /* recursion detected */ __bpf_prog_exit_sleepable_recur(prog, 0, &run_ctx); diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c index 78acf28d4873..53ff50cac61e 100644 --- a/kernel/bpf/trampoline.c +++ b/kernel/bpf/trampoline.c @@ -926,13 +926,12 @@ u64 notrace __bpf_prog_enter_sleepable_recur(struct bpf_prog *prog, migrate_disable(); might_fault(); + run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); + if (unlikely(this_cpu_inc_return(*(prog->active)) != 1)) { bpf_prog_inc_misses_counter(prog); return 0; } - - run_ctx->saved_run_ctx = bpf_set_run_ctx(&run_ctx->run_ctx); - return bpf_prog_start_time(); } |