Re: [PATCH] tracing/eprobe: Replace kzalloc with kmalloc
From: Christophe JAILLET <hidden>
Date: 2023-01-07 08:42:54
Also in:
lkml
Le 07/01/2023 à 04:45, Quanfa Fu a écrit :
quoted hunk ↗ jump to hunk
Since this memory will be filled soon below, I feel that there is no need for a memory of all zeros here. 'snprintf' does not return negative num according to ISO C99, so I feel that no judgment is needed here. No functional change intended. Signed-off-by: Quanfa Fu <redacted> --- kernel/trace/trace_eprobe.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c index 352b65e2b910..cd1d271a74e7 100644 --- a/kernel/trace/trace_eprobe.c +++ b/kernel/trace/trace_eprobe.c@@ -917,15 +917,13 @@ static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const ch for (i = 0; i < argc; i++) len += strlen(argv[i]) + 1; - ep->filter_str = kzalloc(len, GFP_KERNEL); + ep->filter_str = kmalloc(len, GFP_KERNEL); if (!ep->filter_str) return -ENOMEM; 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) {
Hi,
as per [1]:
* The return value is the number of characters which would be
* generated for the given input, excluding the trailing null,
* as per ISO C99. If the return is greater than *or equal* to
* @size, the resulting string is truncated.
So, should this test be:
if (ret >= len)
~~~~
Also, isn't the p[-1] = '\0' after the loop eating the last character?
argc = 1;
argv[0] = "a";
Before the loop:
===============
len = 1 + 1 = 2;
ep->filter_str = 0x00 0x00
^
|___ p
After the loop:
===============
ep->filter_str = 0x61 0x00
^
|___ p
len = 1;
After p[-1]:
============
ep->filter_str = 0x00 0x00
~~ ^
|___ p
Did I miss something obvious?
I don't know the intent here, or if it is an issue at all, but it looks odd.
CJ
[1]: https://elixir.bootlin.com/linux/v6.2-rc1/source/lib/vsprintf.c#L2925ret = -E2BIG; goto error;