On Thu, 3 Jul 2025 13:26:35 +0900 "Masami Hiramatsu (Google)" mhiramat@kernel.org wrote:
From: Masami Hiramatsu (Google) mhiramat@kernel.org
With CONFIG_DEBUG_INFO_BTF=y and PAHOLE_HAS_BTF_TAG=y, `__user` is converted to `__attribute((btf_type_tag("user")))`. In this case, some syscall events have `const char __attribute(...) *` for __user string, like below;
/sys/kernel/tracing # cat events/syscalls/sys_enter_openat/format name: sys_enter_openat ID: 720 format: field:unsigned short common_type; offset:0; size:2; signed:0; field:unsigned char common_flags; offset:2; size:1; signed:0; field:unsigned char common_preempt_count; offset:3; size:1; signed:0; field:int common_pid; offset:4; size:4; signed:1;
field:int __syscall_nr; offset:8; size:4; signed:1; field:int dfd; offset:16; size:8; signed:0; field:const char __attribute__((btf_type_tag("user"))) * filename; offset:24;
Ahh, sorry, it was "__attribute__()" not "__attribute()".
Anyway, I think we should sanitize the __attribute__ from format.
Thank you,
size:8; signed:0;
field:int flags; offset:32; size:8; signed:0; field:umode_t mode; offset:40; size:8; signed:0;
Then the trace event filter failes to set string acceptable flag (FILTER_PTR_STRING) and rejects setting string filter;
# echo 'filename.ustring ~ "*ftracetest-dir.wbx24v*"' >> events/syscalls/sys_enter_openat/filter sh: write error: Invalid argument # cat error_log [ 723.743637] event filter parse error: error: Expecting numeric field Command: filename.ustring ~ "*ftracetest-dir.wbx24v*"
Handle "(const) char __attribute() *" also as string ptr type.
Signed-off-by: Masami Hiramatsu (Google) mhiramat@kernel.org
kernel/trace/trace_events_filter.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 3885aadc434d..5e27190a0377 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -1488,6 +1488,11 @@ int filter_assign_type(const char *type) if (strcmp(type, "char *") == 0 || strcmp(type, "const char *") == 0) return FILTER_PTR_STRING;
- /* Ignore attributes */
- if (glob_match("char __attribute(*) \*", type) ||
glob_match("const char __attribute(*) \\*", type))return FILTER_PTR_STRING;- return FILTER_OTHER;
}