linux-kernel - [PATCH 3/6] kallsyms/bpf: Set module buildid in bpf_address

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Message-ID: <20251105142319.1139183-4-pmladek@suse.com>
Date: Wed,  5 Nov 2025 15:23:15 +0100
From: Petr Mladek <pmladek@...e.com>
To: Petr Pavlu <petr.pavlu@...e.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <kees@...nel.org>
Cc: Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Daniel Gomez <da.gomez@...nel.org>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	linux-modules@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>
Subject: [PATCH 3/6] kallsyms/bpf: Set module buildid in bpf_address_lookup()

Make bpf_address_lookup() compatible with module_address_lookup()
and clear the pointer to @modbuildid together with @modname.

It is not strictly needed because __sprint_symbol() reads @modbuildid
only when @modname is set. But better be on the safe side and make
the API more safe.

Fixes: 9294523e3768 ("module: add printk formats to add module build ID to stacktraces")
Signed-off-by: Petr Mladek <pmladek@...e.com>
---
 include/linux/filter.h | 15 +++++++++++----
 kernel/kallsyms.c      |  4 ++--
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index f5c859b8131a..b7b95840250a 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -1362,12 +1362,18 @@ struct bpf_prog *bpf_prog_ksym_find(unsigned long addr);
 
 static inline int
 bpf_address_lookup(unsigned long addr, unsigned long *size,
-		   unsigned long *off, char **modname, char *sym)
+		   unsigned long *off, char **modname,
+		   const unsigned char **modbuildid, char *sym)
 {
 	int ret = __bpf_address_lookup(addr, size, off, sym);
 
-	if (ret && modname)
-		*modname = NULL;
+	if (ret) {
+		if (modname)
+			*modname = NULL;
+		if (modbuildid)
+			*modbuildid = NULL;
+	}
+
 	return ret;
 }
 
@@ -1433,7 +1439,8 @@ static inline struct bpf_prog *bpf_prog_ksym_find(unsigned long addr)
 
 static inline int
 bpf_address_lookup(unsigned long addr, unsigned long *size,
-		   unsigned long *off, char **modname, char *sym)
+		   unsigned long *off, char **modname,
+		   const unsigned char **modbuildid, char *sym)
 {
 	return 0;
 }
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 9455e3bb07fc..efb12b077220 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -374,8 +374,8 @@ static int kallsyms_lookup_buildid(unsigned long addr,
 	ret = module_address_lookup(addr, symbolsize, offset,
 				    modname, modbuildid, namebuf);
 	if (!ret)
-		ret = bpf_address_lookup(addr, symbolsize,
-					 offset, modname, namebuf);
+		ret = bpf_address_lookup(addr, symbolsize, offset,
+					 modname, modbuildid, namebuf);
 
 	if (!ret)
 		ret = ftrace_mod_address_lookup(addr, symbolsize,
-- 
2.51.1