Re: [PATCH AUTOSEL 5.5 12/28] staging: greybus: loopback_test: fix potential path truncation

[Greg KH]

On Thu, Mar 26, 2020 at 07:23:41PM -0400, Sasha Levin wrote:
> From: Johan Hovold <johan@xxxxxxxxxx>
> 
> [ Upstream commit f16023834863932f95dfad13fac3fc47f77d2f29 ]
> 
> Newer GCC warns about a possible truncation of a generated sysfs path
> name as we're concatenating a directory path with a file name and
> placing the result in a buffer that is half the size of the maximum
> length of the directory path (which is user controlled).
> 
> loopback_test.c: In function 'open_poll_files':
> loopback_test.c:651:31: warning: '%s' directive output may be truncated writing up to 511 bytes into a region of size 255 [-Wformat-truncation=]
>   651 |   snprintf(buf, sizeof(buf), "%s%s", dev->sysfs_entry, "iteration_count");
>       |                               ^~
> loopback_test.c:651:3: note: 'snprintf' output between 16 and 527 bytes into a destination of size 255
>   651 |   snprintf(buf, sizeof(buf), "%s%s", dev->sysfs_entry, "iteration_count");
>       |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Fix this by making sure the buffer is large enough the concatenated
> strings.
> 
> Fixes: 6b0658f68786 ("greybus: tools: Add tools directory to greybus repo and add loopback")
> Fixes: 9250c0ee2626 ("greybus: Loopback_test: use poll instead of inotify")
> Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20200312110151.22028-3-johan@xxxxxxxxxx
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
>  drivers/staging/greybus/tools/loopback_test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/greybus/tools/loopback_test.c b/drivers/staging/greybus/tools/loopback_test.c
> index ba6f905f26fad..5ce7d6fa086cc 100644
> --- a/drivers/staging/greybus/tools/loopback_test.c
> +++ b/drivers/staging/greybus/tools/loopback_test.c
> @@ -637,7 +637,7 @@ int find_loopback_devices(struct loopback_test *t)
>  static int open_poll_files(struct loopback_test *t)
>  {
>  	struct loopback_device *dev;
> -	char buf[MAX_STR_LEN];
> +	char buf[MAX_SYSFS_PATH + MAX_STR_LEN];
>  	char dummy;
>  	int fds_idx = 0;
>  	int i;
> -- 
> 2.20.1
> 

Already in all stable releases, so no need to add it again.