[PATCH bpf-next v6 1/2] tracing: Prefer vmlinux symbols over module symbols for unqualified kprobes

Andrey Grodzovsky
2026-04-07T16:52:12Z

When an unqualified kprobe target exists in both vmlinux and a loaded
module, number_of_same_symbols() returns a count greater than 1,
causing kprobe attachment to fail with -EADDRNOTAVAIL even though the
vmlinux symbol is unambiguous.

When no module qualifier is given and the symbol is found in vmlinux,
return the vmlinux-only count without scanning loaded modules. This
preserves the existing behavior for all other cases:
- Symbol only in a module: vmlinux count is 0, falls through to module
scan as before.
- Symbol qualified with MOD:SYM: mod != NULL, unchanged path.
- Symbol ambiguous within vmlinux itself: count > 1 is returned as-is.

Fixes: 926fe783c8a6 ("tracing/kprobes: Fix symbol counting logic by looking at modules as well")
Fixes: 9d8616034f16 ("tracing/kprobes: Add symbol counting check when module loads")
Suggested-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@crowdstrike.com>
---
kernel/trace/trace_kprobe.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index a5dbb72528e0..99c41ea8b6d7 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -765,6 +765,13 @@ static unsigned int number_of_same_symbols(const char *mod, const char *func_nam
if (!mod)
kallsyms_on_each_match_symbol(count_symbols, func_name, &ctx.count);

+ /* If the symbol is found in vmlinux, use vmlinux resolution only.
+ * This prevents module symbols from shadowing vmlinux symbols
+ * and causing -EADDRNOTAVAIL for unqualified kprobe targets.
+ */
+ if (!mod && ctx.count > 0)
+ return ctx.count;
+
module_kallsyms_on_each_symbol(mod, count_mod_symbols, &ctx);

return ctx.count;
--
2.34.1