Re: [PATCHv2 4/4] mkfs: avoid heap-buffer-read-underrun for zero-length "size" arg

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On Fri, Apr 20, 2012 at 09:27:26PM +0200, Jim Meyering wrote:
> From: Jim Meyering <meyering@xxxxxxxxxx>
> 
> * mkfs.c (parse_size): ./mkfs.btrfs -A '' would read and possibly
> write the byte before beginning of strdup'd heap buffer.  All other
> size-accepting options were similarly affected.
> 
> Reviewed-by: Josef Bacik <josef@xxxxxxxxxx>
> ---
>  cmds-subvolume.c |    2 +-
>  mkfs.c           |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/cmds-subvolume.c b/cmds-subvolume.c
> index fc749f1..a01c830 100644
> --- a/cmds-subvolume.c
> +++ b/cmds-subvolume.c
> @@ -380,7 +380,7 @@ static int cmd_snapshot(int argc, char **argv)
> 
>  	args.fd = fd;
>  	strncpy(args.name, newname, BTRFS_SUBVOL_NAME_MAX);
                                                     ^ +1

> -	args.name[BTRFS_PATH_NAME_MAX-1] = 0;
> +	args.name[BTRFS_SUBVOL_NAME_MAX-1] = 0;
 
   args.name[BTRFS_SUBVOL_NAME_MAX] = 0;

>  	res = ioctl(fddst, BTRFS_IOC_SNAP_CREATE_V2, &args);
>  	e = errno;
> 
> diff --git a/mkfs.c b/mkfs.c
> index 03239fb..4aff2fd 100644
> --- a/mkfs.c
> +++ b/mkfs.c
> @@ -63,7 +63,7 @@ static u64 parse_size(char *s)
> 
>  	s = strdup(s);
> 
> -	if (!isdigit(s[len - 1])) {
> +	if (len && !isdigit(s[len - 1])) {

   I think I'd prefer that len is a size_t, not an int here. (Or that
len is tested to be >0).

>  		c = tolower(s[len - 1]);
>  		switch (c) {
>  		case 'g':

   Hugo.

-- 
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