2023-01-09 03:46:56

by Quanfa Fu

Subject: [PATCH v2] tracing/eprobe: Replace snprintf with memcpy

No need to check for negative return value from snprintf() as the
code does not return negative values. Replace snprintf with memcpy.

Signed-off-by: Quanfa Fu <[email protected]>

-----
V1 -> V2: memory allc uses kzalloc and replace snprintf with memcpy
---
kernel/trace/trace_eprobe.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index 352b65e2b910..56eb39f495f6 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -905,7 +905,7 @@ static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[
static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const char *argv[])
{
struct event_filter *dummy = NULL;
- int i, ret, len = 0;
+ int i, ret, arg_len, len = 0;
char *p;

if (argc == 0) {
@@ -923,17 +923,17 @@ static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const ch

p = ep->filter_str;
for (i = 0; i < argc; i++) {
- ret = snprintf(p, len, "%s ", argv[i]);
- if (ret < 0)
- goto error;
- if (ret > len) {
- ret = -E2BIG;
- goto error;
- }
- p += ret;
- len -= ret;
+ arg_len = strlen(argv[i]);
+ memcpy((void *)p, argv[i], arg_len);
+
+ if (i == argc - 1)
+ p[arg_len] = '\0';
+ else
+ p[arg_len] = ' ';
+
+ p += arg_len + 1;
+ len -= arg_len + 1;
}
- p[-1] = '\0';

/*
* Ensure the filter string can be parsed correctly. Note, this
--
2.31.1

2023-01-09 04:06:51

by Steven Rostedt

Subject: Re: [PATCH v2] tracing/eprobe: Replace snprintf with memcpy

On Mon, 9 Jan 2023 11:32:13 +0800
Quanfa Fu <[email protected]> wrote:

> @@ -923,17 +923,17 @@ static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const ch
>
> p = ep->filter_str;
> for (i = 0; i < argc; i++) {
> - ret = snprintf(p, len, "%s ", argv[i]);
> - if (ret < 0)
> - goto error;
> - if (ret > len) {
> - ret = -E2BIG;
> - goto error;
> - }
> - p += ret;
> - len -= ret;
> + arg_len = strlen(argv[i]);
> + memcpy((void *)p, argv[i], arg_len);
> +
> + if (i == argc - 1)
> + p[arg_len] = '\0';
> + else
> + p[arg_len] = ' ';
> +
> + p += arg_len + 1;
> + len -= arg_len + 1;
> }

The above is too complex. I mentioned strncat() but you could still
just keep snprintf() too, which adds the '\0';

for (i = 0; i < argc; i++) {
if (i)
ret = snprintf(p, len, " %s", argv[i]);
else
ret = snprintf(p, len, "%s", argv[i]);
p += ret;
len -= ret;
}

-- Steve

> - p[-1] = '\0';
>
> /*
> * Ensure the filter string can be parsed correctly. Note, this

2023-01-09 05:05:39

by Quanfa Fu

Subject: Re: [PATCH v2] tracing/eprobe: Replace snprintf with memcpy

Thanks, I'll check it out.
Thanks !!

On Mon, Jan 9, 2023 at 11:52 AM Steven Rostedt <[email protected]> wrote:
>
> On Mon, 9 Jan 2023 11:32:13 +0800
> Quanfa Fu <[email protected]> wrote:
>
> > @@ -923,17 +923,17 @@ static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const ch
> >
> > p = ep->filter_str;
> > for (i = 0; i < argc; i++) {
> > - ret = snprintf(p, len, "%s ", argv[i]);
> > - if (ret < 0)
> > - goto error;
> > - if (ret > len) {
> > - ret = -E2BIG;
> > - goto error;
> > - }
> > - p += ret;
> > - len -= ret;
> > + arg_len = strlen(argv[i]);
> > + memcpy((void *)p, argv[i], arg_len);
> > +
> > + if (i == argc - 1)
> > + p[arg_len] = '\0';
> > + else
> > + p[arg_len] = ' ';
> > +
> > + p += arg_len + 1;
> > + len -= arg_len + 1;
> > }
>
> The above is too complex. I mentioned strncat() but you could still
> just keep snprintf() too, which adds the '\0';
>
> for (i = 0; i < argc; i++) {
> if (i)
> ret = snprintf(p, len, " %s", argv[i]);
> else
> ret = snprintf(p, len, "%s", argv[i]);
> p += ret;
> len -= ret;
> }
>
> -- Steve
>
> > - p[-1] = '\0';
> >
> > /*
> > * Ensure the filter string can be parsed correctly. Note, this