Re: [PATCH] tracing: use strlcpy instead of strncpy

Frederic Weisbecker
2009-05-19T23:43:27Z

On Tue, May 19, 2009 at 09:51:50AM +0800, Lai Jiangshan wrote:
> strlcpy() will add '\0' for the copied string.
>
> [Impact] cleanup

As Stefan said, the impact line and the changelog is omitting
a possible side effect.

>
> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index 05b4747..9359e85 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -434,8 +434,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
> if (!buts->buf_size || !buts->buf_nr)
> return -EINVAL;
>
> - strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
> - buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';
> + strlcpy(buts->name, name, BLKTRACE_BDEV_SIZE);
>
> /*
> * some device names have larger paths - convert the slashes
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 665a915..2484555 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -133,7 +133,7 @@ static char *default_bootup_tracer;
>
> static int __init set_ftrace(char *str)
> {
> - strncpy(bootup_tracer_buf, str, BOOTUP_TRACER_SIZE);
> + strlcpy(bootup_tracer_buf, str, BOOTUP_TRACER_SIZE);
> default_bootup_tracer = bootup_tracer_buf;
> /* We are using ftrace early, expand it */
> ring_buffer_expanded = 1;
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 6e735d4..e08c952 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -155,8 +155,8 @@ struct trace_boot_ret {
> struct trace_branch {
> struct trace_entry ent;
> unsigned line;
> - char func[TRACE_FUNC_SIZE+1];
> - char file[TRACE_FILE_SIZE+1];
> + char func[TRACE_FUNC_SIZE];
> + char file[TRACE_FILE_SIZE];

Although I don't think this is that much risky, this is the possible
side effect: we are loosing a character.

I guess it's fine, the CPP constants here seem to be just magic
assumptions (func_size = 30, file_size = 20), it just needs to be
mentioned in the changelog for future possible bug tracking.

Thanks,
Frederic.

> char correct;
> };
>
> diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
> index 7a7a9fd..a84e036 100644
> --- a/kernel/trace/trace_branch.c
> +++ b/kernel/trace/trace_branch.c
> @@ -67,10 +67,8 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
> p--;
> p++;
>
> - strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
> - strncpy(entry->file, p, TRACE_FILE_SIZE);
> - entry->func[TRACE_FUNC_SIZE] = 0;
> - entry->file[TRACE_FILE_SIZE] = 0;
> + strlcpy(entry->func, f->func, TRACE_FUNC_SIZE);
> + strlcpy(entry->file, p, TRACE_FILE_SIZE);
> entry->line = f->line;
> entry->correct = val == expect;
>
> diff --git a/kernel/trace/trace_event_types.h b/kernel/trace/trace_event_types.h
> index 5e32e37..2ae6679 100644
> --- a/kernel/trace/trace_event_types.h
> +++ b/kernel/trace/trace_event_types.h
> @@ -122,10 +122,10 @@ TRACE_EVENT_FORMAT(print, TRACE_PRINT, print_entry, ignore,
> TRACE_EVENT_FORMAT(branch, TRACE_BRANCH, trace_branch, ignore,
> TRACE_STRUCT(
> TRACE_FIELD(unsigned int, line, line)
> - TRACE_FIELD_SPECIAL(char func[TRACE_FUNC_SIZE+1], func,
> - TRACE_FUNC_SIZE+1, func)
> - TRACE_FIELD_SPECIAL(char file[TRACE_FUNC_SIZE+1], file,
> - TRACE_FUNC_SIZE+1, file)
> + TRACE_FIELD_SPECIAL(char func[TRACE_FUNC_SIZE], func,
> + TRACE_FUNC_SIZE, func)
> + TRACE_FIELD_SPECIAL(char file[TRACE_FUNC_SIZE], file,
> + TRACE_FUNC_SIZE, file)
> TRACE_FIELD(char, correct, correct)
> ),
> TP_RAW_FMT("%u:%s:%s (%u)")
>
> --
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