[PATCH 5.8 321/633] tracing: Handle synthetic event array field type checking correctly

Greg Kroah-Hartman
2020-10-27T15:11:10Z

From: Tom Zanussi <zanussi@kernel.org>

[ Upstream commit 10819e25799aae564005b6049a45e9808797b3bb ]

Since synthetic event array types are derived from the field name,
there may be a semicolon at the end of the type which should be
stripped off.

If there are more characters following that, normal type string
checking will result in an invalid type.

Without this patch, you can end up with an invalid field type string
that gets displayed in both the synthetic event description and the
event format:

Before:

# echo 'myevent char str[16]; int v' >> synthetic_events
# cat synthetic_events
myevent char[16]; str; int v

name: myevent
ID: 1936
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:char str[16];; offset:8; size:16; signed:1;
field:int v; offset:40; size:4; signed:1;

print fmt: "str=%s, v=%d", REC->str, REC->v

After:

# echo 'myevent char str[16]; int v' >> synthetic_events
# cat synthetic_events
myevent char[16] str; int v

# cat events/synthetic/myevent/format
name: myevent
ID: 1936
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:char str[16]; offset:8; size:16; signed:1;
field:int v; offset:40; size:4; signed:1;

print fmt: "str=%s, v=%d", REC->str, REC->v

Link: https://lkml.kernel.org/r/6587663b56c2d45ab9d8c8472a2110713cdec97d.1602598160.git.zanussi@kernel.org

[ <rostedt@goodmis.org>: wrote parse_synth_field() snippet. ]
Fixes: 4b147936fa50 (tracing: Add support for 'synthetic' events)
Reported-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/trace/trace_events_synth.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 46a96686e93c6..c8892156db341 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -132,7 +132,7 @@ static int synth_field_string_size(char *type)
start += sizeof("char[") - 1;

end = strchr(type, ']');
- if (!end || end < start)
+ if (!end || end < start || type + strlen(type) > end + 1)
return -EINVAL;

len = end - start;
@@ -502,8 +502,14 @@ static struct synth_field *parse_synth_field(int argc, const char **argv,
if (field_type[0] == ';')
field_type++;
len = strlen(field_type) + 1;
- if (array)
- len += strlen(array);
+
+ if (array) {
+ int l = strlen(array);
+
+ if (l && array[l - 1] == ';')
+ l--;
+ len += l;
+ }
if (prefix)
len += strlen(prefix);

--
2.25.1