[PATCH 1/1] fs: fix smh_fs_read_at()

[Sean Anderson]

On 5/17/23 06:23, Heinrich Schuchardt wrote:
> The return value of smh_flen() is written to size and not to ret. But ret
> is checked. We can avoid calling smh_flen() by setting maxsize to LONG_MAX
> if it is not set yet.
> 
> Check input parameters.
> 
> Fixes: f676b45151c3 ("fs: Add semihosting filesystem")
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> ---
>  fs/semihostingfs.c | 14 +++++---------
>  1 file changed, 5 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/semihostingfs.c b/fs/semihostingfs.c
> index 96eb3349a2..8a7d4da884 100644
> --- a/fs/semihostingfs.c
> +++ b/fs/semihostingfs.c
> @@ -25,6 +25,9 @@ static int smh_fs_read_at(const char *filename, loff_t pos, void *buffer,
>  {
>  	long fd, size, ret;
>  
> +	if (pos > LONG_MAX || maxsize > LONG_MAX)

Should be ULONG_MAX. The type should really be ulong but isn't.

> +		return -EINVAL;
> +
>  	fd = smh_open(filename, MODE_READ | MODE_BINARY);
>  	if (fd < 0)
>  		return fd;
> @@ -33,15 +36,8 @@ static int smh_fs_read_at(const char *filename, loff_t pos, void *buffer,
>  		smh_close(fd);
>  		return ret;
>  	}
> -	if (!maxsize) {
> -		size = smh_flen(fd);
> -		if (ret < 0) {
> -			smh_close(fd);
> -			return size;
> -		}
> -
> -		maxsize = size;
> -	}
> +	if (!maxsize)
> +		maxsize = LONG_MAX;

Same here.

>  
>  	size = smh_read(fd, buffer, maxsize);
>  	smh_close(fd);

This interface is nuts, but this patch does successfully implement it...

--Sean