Re: [PATCH] db/print: bad character cause illegal memory access

[Brian Foster <bfoster@redhat.com>]

On Tue, Jan 09, 2018 at 02:20:27PM +0800, Zorro Lang wrote:
> xfs_db can print specified field values, likes:
>   # xfs_db -c "inode $inum" -c "print core.nblocks" $dev
> 
> But when we give it some bad chararcters, the 'print' command will
> crash:
> 
>   # xfs_db -r -c "inode 67211167" -c "print core.*" /dev/mapper/rhel-root
>   bad character in field *
>   *** Error in `xfs_db': free(): invalid pointer: 0x00007fa116e937b8 ***
>   ...
>   (crash messages)
>   ...
>   # xfs_db -r -c "inode 67211167" -c "print core.\"" /dev/mapper/rhel-root
>   missing closing quote
>   *** Error in `xfs_db': free(): invalid pointer: 0x00007f6e8e3c37b8 ***
>   ...
>   (crash messages)
>   ...
> 
> The reason is xfs_db call ftok_free() to free ftok_t list, but
> flist_split() forgets to set the tail to NULL. That cause ftok_free()
> trys to free illegal memory address.
> 
> Signed-off-by: Zorro Lang <zlang@redhat.com>
> ---
>  db/flist.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/db/flist.c b/db/flist.c
> index e11acbfc..1a875b95 100644
> --- a/db/flist.c
> +++ b/db/flist.c
> @@ -371,11 +371,14 @@ flist_split(
>  	v = xmalloc(sizeof(*v));
>  	v->tok = NULL;
>  	while (*s) {
> +		v = xrealloc(v, (nv + 1) * sizeof(*v));
>  		/* need to add string handling */
>  		if (*s == '\"') {
>  			s++; /* skip first quote */
>  			if ((a = strrchr(s, '\"')) == NULL) {
>  				dbprintf(_("missing closing quote %s\n"), s);
> +				v[nv].tok = NULL;
> +				v[nv].tokty = TT_END;
>  				ftok_free(v);
>  				return NULL;
>  			}
> @@ -393,19 +396,21 @@ flist_split(
>  			t = puncttypes[a - punctchars];
>  		} else {
>  			dbprintf(_("bad character in field %s\n"), s);
> +			v[nv].tok = NULL;
> +			v[nv].tokty = TT_END;
>  			ftok_free(v);
>  			return NULL;
>  		}
>  		a = xmalloc(l + 1);
>  		strncpy(a, s, l);
>  		a[l] = '\0';
> -		v = xrealloc(v, (nv + 2) * sizeof(*v));
>  		v[nv].tok = a;
>  		v[nv].tokty = t;
>  		nv++;
>  		s += l + tailskip;
>  		tailskip = 0;
>  	}
> +	v = xrealloc(v, (nv + 1) * sizeof(*v));
>  	v[nv].tok = NULL;

Could we just move the above line into the loop (right after nv is
bumped) to initialize .tok similar to the initial allocation before the
loop?

Brian

>  	v[nv].tokty = TT_END;
>  	return v;
> -- 
> 2.13.6
> 
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