linux-kernel - [PATCH v2] perf/bpf: Don't call bpf_overflow

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20240813151727.28797-1-jdamato@fastly.com>
Date: Tue, 13 Aug 2024 15:17:27 +0000
From: Joe Damato <jdamato@...tly.com>
To: linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org
Cc: peterz@...radead.org,
	andrii@...nel.org,
	mhiramat@...nel.org,
	olsajiri@...il.com,
	me@...ehuey.com,
	Kyle Huey <khuey@...ehuey.com>,
	Andrii Nakryiko <andrii.nakryiko@...il.com>,
	Joe Damato <jdamato@...tly.com>,
	stable@...r.kernel.org
Subject: [PATCH v2] perf/bpf: Don't call bpf_overflow_handler() for tracing events

From: Kyle Huey <me@...ehuey.com>

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 <khuey@...ehuey.com>
Suggested-by: Andrii Nakryiko <andrii.nakryiko@...il.com>
Reported-by: Joe Damato <jdamato@...tly.com>
Closes: https://lore.kernel.org/lkml/ZpFfocvyF3KHaSzF@LQ3V64L9R2/
Fixes: f11f10bfa1ca ("perf/bpf: Call BPF handler directly, not through overflow machinery")
Cc: stable@...r.kernel.org
Tested-by: Joe Damato <jdamato@...tly.com> # bpftrace
---
v2:
  - Update patch based on Andrii's suggestion
  - Update commit message

 kernel/events/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

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;

 	/*
-- 
2.25.1