2014-07-26 14:43:30

by Rickard Strandqvist

Subject: [PATCH] kernel: debug: kdb: kdb_io.c: Cleaning up missing null-terminate in conjunction with strncpy

Replacing strncpy with strlcpy to avoid strings that lacks null terminate.

Signed-off-by: Rickard Strandqvist <[email protected]>
---
kernel/debug/kdb/kdb_io.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index 7c70812..27977c0 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -361,9 +361,9 @@ poll_again:
kdb_printf("%s", buffer);
} else if (tab != 2 && count > 0) {
len_tmp = strlen(p_tmp);
- strncpy(p_tmp+len_tmp, cp, lastchar-cp+1);
+ strlcpy(p_tmp+len_tmp, cp, lastchar-cp+1);
len_tmp = strlen(p_tmp);
- strncpy(cp, p_tmp+len, len_tmp-len + 1);
+ strlcpy(cp, p_tmp+len, len_tmp-len + 1);
len = len_tmp - len;
kdb_printf("%s", cp);
cp += len;
@@ -442,7 +442,7 @@ poll_again:
char *kdb_getstr(char *buffer, size_t bufsize, char *prompt)
{
if (prompt && kdb_prompt_str != prompt)
- strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
+ strlcpy(kdb_prompt_str, prompt, CMD_BUFLEN);
kdb_printf(kdb_prompt_str);
kdb_nextline = 1; /* Prompt and input resets line number */
return kdb_read(buffer, bufsize);
--
1.7.10.4

2014-07-28 14:18:09

by Kees Cook

Subject: Re: [PATCH] kernel: debug: kdb: kdb_io.c: Cleaning up missing null-terminate in conjunction with strncpy

On Sat, Jul 26, 2014 at 10:44 AM, Rickard Strandqvist
<[email protected]> wrote:
> Replacing strncpy with strlcpy to avoid strings that lacks null terminate.
>
> Signed-off-by: Rickard Strandqvist <[email protected]>
> ---
> kernel/debug/kdb/kdb_io.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
> index 7c70812..27977c0 100644
> --- a/kernel/debug/kdb/kdb_io.c
> +++ b/kernel/debug/kdb/kdb_io.c
> @@ -361,9 +361,9 @@ poll_again:
> kdb_printf("%s", buffer);
> } else if (tab != 2 && count > 0) {
> len_tmp = strlen(p_tmp);
> - strncpy(p_tmp+len_tmp, cp, lastchar-cp+1);
> + strlcpy(p_tmp+len_tmp, cp, lastchar-cp+1);
> len_tmp = strlen(p_tmp);
> - strncpy(cp, p_tmp+len, len_tmp-len + 1);
> + strlcpy(cp, p_tmp+len, len_tmp-len + 1);
> len = len_tmp - len;
> kdb_printf("%s", cp);
> cp += len;

It's not clear to me what this code is actually doing, but I think the
"+1" parts to these strncpy()s are there to include the NULL
character.

> @@ -442,7 +442,7 @@ poll_again:
> char *kdb_getstr(char *buffer, size_t bufsize, char *prompt)
> {
> if (prompt && kdb_prompt_str != prompt)
> - strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
> + strlcpy(kdb_prompt_str, prompt, CMD_BUFLEN);

This seems like a good idea.

> kdb_printf(kdb_prompt_str);
> kdb_nextline = 1; /* Prompt and input resets line number */
> return kdb_read(buffer, bufsize);
> --
> 1.7.10.4
>

-Kees

--
Kees Cook
Chrome OS Security