[PATCH] terminate readlink result string

[PATCH] terminate readlink result string

[Tobias Stoeckmann]

readlink does not guarantee that its result string is nul-terminated.
Instead, increase the buffer by one byte to make sure that we can
add '\0' at the end.
---
 alsactl/init_sysfs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/alsactl/init_sysfs.c b/alsactl/init_sysfs.c
index 0cbada2..5c789b6 100644
--- a/alsactl/init_sysfs.c
+++ b/alsactl/init_sysfs.c
@@ -108,11 +108,11 @@ static char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
 
 	if (S_ISLNK(statbuf.st_mode)) {
 		/* links return the last element of the target path */
-		char link_target[PATH_SIZE];
+		char link_target[PATH_SIZE + 1];
 		int len;
 		const char *pos;
 
-		len = readlink(path_full, link_target, sizeof(link_target));
+		len = readlink(path_full, link_target, sizeof(link_target) - 1);
 		if (len > 0) {
 			link_target[len] = '\0';
 			pos = strrchr(link_target, '/');
-- 
2.4.5

Re: [PATCH] terminate readlink result string

[Takashi Iwai]

On Sat, 11 Jul 2015 13:23:57 +0200,
Tobias Stoeckmann wrote:
> 
> readlink does not guarantee that its result string is nul-terminated.
> Instead, increase the buffer by one byte to make sure that we can
> add '\0' at the end.

Applied, thanks.


Takashi

> ---
>  alsactl/init_sysfs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/alsactl/init_sysfs.c b/alsactl/init_sysfs.c
> index 0cbada2..5c789b6 100644
> --- a/alsactl/init_sysfs.c
> +++ b/alsactl/init_sysfs.c
> @@ -108,11 +108,11 @@ static char *sysfs_attr_get_value(const char *devpath, const char *attr_name)
>  
>  	if (S_ISLNK(statbuf.st_mode)) {
>  		/* links return the last element of the target path */
> -		char link_target[PATH_SIZE];
> +		char link_target[PATH_SIZE + 1];
>  		int len;
>  		const char *pos;
>  
> -		len = readlink(path_full, link_target, sizeof(link_target));
> +		len = readlink(path_full, link_target, sizeof(link_target) - 1);
>  		if (len > 0) {
>  			link_target[len] = '\0';
>  			pos = strrchr(link_target, '/');
> -- 
> 2.4.5
> 
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