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Subject[PATCH v2] event-parse: Zero should not be considered "not found" in eval_flag()

Guilherme Cox found that:
There is, however, a potential bug if there is an item with code zero
that is not the first one in the symbol list, since eval_flag(..)
returns 0 when it doesn't find anything.

That is, if you have the following enums:

enum {
FOO_START = 0,
FOO_GO = 1,
FOO_END = 2
}

and then have:

__print_symbolic(foo, FOO_GO, "go", FOO_START, "start",
FOO_END, "end")

If none of the enums are known to pevent, then eval_flag() will return
zero, and it will match it to the first item in the list, which would
be FOO_GO, which is not zero.

Luckily, in most cases, the first element would be zero, and the parsing
would match out of sheer luck.

Reported-by: Guilherme Cox <cox@computer.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
v2 - fixed "From:" and give a bit more info in the change log. I also
created an event that I could test this issue with.

event-parse.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/event-parse.c b/event-parse.c
index aff743710001..f2fb50141703 100644
--- a/event-parse.c
+++ b/event-parse.c
@@ -3576,7 +3576,7 @@ static const struct flag flags[] = {
{ "HRTIMER_RESTART", 1 },
};

-static unsigned long long eval_flag(const char *flag)
+static long long eval_flag(const char *flag)
{
int i;

@@ -3592,7 +3592,7 @@ static unsigned long long eval_flag(const char *flag)
if (strcmp(flags[i].name, flag) == 0)
return flags[i].value;

- return 0;
+ return -1LL;
}

static void print_str_to_seq(struct trace_seq *s, const char *format,
@@ -3666,7 +3666,7 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
struct print_flag_sym *flag;
struct format_field *field;
struct printk_map *printk;
- unsigned long long val, fval;
+ long long val, fval;
unsigned long addr;
char *str;
unsigned char *hex;
@@ -3725,11 +3725,11 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
print = 0;
for (flag = arg->flags.flags; flag; flag = flag->next) {
fval = eval_flag(flag->value);
- if (!val && !fval) {
+ if (!val && fval < 0) {
print_str_to_seq(s, format, len_arg, flag->str);
break;
}
- if (fval && (val & fval) == fval) {
+ if (fval > 0 && (val & fval) == fval) {
if (print && arg->flags.delim)
trace_seq_puts(s, arg->flags.delim);
print_str_to_seq(s, format, len_arg, flag->str);
--
1.8.3.1


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