linux-kernel - [PATCH] bpf: Don't use %pK through printk

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Message-Id: <20250811-restricted-pointers-bpf-v1-1-a1d7cc3cb9e7@linutronix.de>
Date: Mon, 11 Aug 2025 14:08:04 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, 
 Martin KaFai Lau <martin.lau@...ux.dev>, 
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
 Yonghong Song <yonghong.song@...ux.dev>, 
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, 
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
 Jiri Olsa <jolsa@...nel.org>
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH] bpf: Don't use %pK through printk

In the past %pK was preferable to %p as it would not leak raw pointer
values into the kernel log.
Since commit ad67b74d2469 ("printk: hash addresses printed with %p")
the regular %p has been improved to avoid this issue.
Furthermore, restricted pointers ("%pK") were never meant to be used
through printk(). They can still unintentionally leak raw pointers or
acquire sleeping locks in atomic contexts.

Switch to the regular pointer formatting which is safer and
easier to reason about.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
 include/linux/filter.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 1e7fd3ee759e07534eee7d8b48cffa1dfea056fb..52fecb7a1fe36d233328aabbe5eadcbd7e07cc5a 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1296,7 +1296,7 @@ void bpf_jit_prog_release_other(struct bpf_prog *fp, struct bpf_prog *fp_other);
 static inline void bpf_jit_dump(unsigned int flen, unsigned int proglen,
 				u32 pass, void *image)
 {
-	pr_err("flen=%u proglen=%u pass=%u image=%pK from=%s pid=%d\n", flen,
+	pr_err("flen=%u proglen=%u pass=%u image=%p from=%s pid=%d\n", flen,
 	       proglen, pass, image, current->comm, task_pid_nr(current));
 
 	if (image)

---
base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585
change-id: 20250811-restricted-pointers-bpf-04da04ea1b8a

Best regards,
-- 
Thomas Weißschuh <thomas.weissschuh@...utronix.de>