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[v7,bpf-next,04/10] bpf: Protect probed address based on kptr_restrict setting

Message ID 20230709025630.3735-5-laoar.shao@gmail.com (mailing list archive)
State Accepted
Commit f1a414537ecc18b5882a57045ce3e4a11e528290
Headers show
Series bpf: Support ->fill_link_info for kprobe_multi and perf_event links | expand

Commit Message

Yafang Shao July 9, 2023, 2:56 a.m. UTC 
The probed address can be accessed by userspace through querying the task
file descriptor (fd). However, it is crucial to adhere to the kptr_restrict
setting and refrain from exposing the address if it is not permitted.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/trace/trace_kprobe.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
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Patch

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 1b3fa7b854aa..249eb14d0f7a 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1551,7 +1551,10 @@  int bpf_get_kprobe_info(const struct perf_event *event, u32 *fd_type,
 	} else {
 		*symbol = NULL;
 		*probe_offset = 0;
-		*probe_addr = (unsigned long)tk->rp.kp.addr;
+		if (kallsyms_show_value(current_cred()))
+			*probe_addr = (unsigned long)tk->rp.kp.addr;
+		else
+			*probe_addr = 0;
 	}
 	return 0;
 }