From: Kyle Huey Date: Tue, 13 Aug 2024 15:17:27 +0000 (+0000) Subject: perf/bpf: Don't call bpf_overflow_handler() for tracing events X-Git-Tag: v6.11-pxa1908~205^2 X-Git-Url: https://git.dujemihanovic.xyz/?a=commitdiff_plain;h=100bff23818eb61751ed05d64a7df36ce9728a4d;p=linux.git perf/bpf: Don't call bpf_overflow_handler() for tracing events The regressing commit is new in 6.10. It assumed that anytime event->prog is set bpf_overflow_handler() should be invoked to execute the attached bpf program. This assumption is false for tracing events, and as a result the regressing commit broke bpftrace by invoking the bpf handler with garbage inputs on overflow. Prior to the regression the overflow handlers formed a chain (of length 0, 1, or 2) and perf_event_set_bpf_handler() (the !tracing case) added bpf_overflow_handler() to that chain, while perf_event_attach_bpf_prog() (the tracing case) did not. Both set event->prog. The chain of overflow handlers was replaced by a single overflow handler slot and a fixed call to bpf_overflow_handler() when appropriate. This modifies the condition there to check event->prog->type == BPF_PROG_TYPE_PERF_EVENT, restoring the previous behavior and fixing bpftrace. Signed-off-by: Kyle Huey Suggested-by: Andrii Nakryiko Reported-by: Joe Damato Closes: https://lore.kernel.org/lkml/ZpFfocvyF3KHaSzF@LQ3V64L9R2/ Fixes: f11f10bfa1ca ("perf/bpf: Call BPF handler directly, not through overflow machinery") Cc: stable@vger.kernel.org Tested-by: Joe Damato # bpftrace Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/r/20240813151727.28797-1-jdamato@fastly.com Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/events/core.c b/kernel/events/core.c index aa3450bdc227..c973e3c11e03 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9706,7 +9706,8 @@ static int __perf_event_overflow(struct perf_event *event, ret = __perf_event_account_interrupt(event, throttle); - if (event->prog && !bpf_overflow_handler(event, data, regs)) + if (event->prog && event->prog->type == BPF_PROG_TYPE_PERF_EVENT && + !bpf_overflow_handler(event, data, regs)) return ret; /*