[PATCH] TUI: Fix buffer overflow in tui_expand_tabs

[Anton Blanchard]

Hi,

> tui_expand_tabs writes past the end of the buffers it allocates
> because we forget to zero out col. This results in us adding more
> spaces than we need to get aligned, and we write past the end of the
> allocated buffer.
> 
> This was noticed on Ubuntu Vivid ppc64le, where gdb would SEGV when
> using the TUI.

Any feedback on this? We either need to fix it, or back out commit
312809f88389 ("Make sure TABs are expanded in TUI windows on
MS-Windows.")

Anton

> 2015-03-17  Anton Blanchard  <anton@samba.org>
> 
> gdb/ChangeLog:
> 	* tui/tui-io.c (tui_expand_tabs): Zero col before reusing.
> ---
>  gdb/ChangeLog    | 4 ++++
>  gdb/tui/tui-io.c | 2 +-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index d984565..4e0177a 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,7 @@
> +2015-03-17  Anton Blanchard  <anton@samba.org>
> +
> +	* tui/tui-io.c (tui_expand_tabs): Zero col before reusing.
> +
>  2015-03-16  John Baldwin  <jhb@FreeBSD.org>
>  
>  	* fbsd-tdep.c (fbsd_make_corefile_notes): Fetch all target
> registers diff --git a/gdb/tui/tui-io.c b/gdb/tui/tui-io.c
> index a8af9b6..02ae17d 100644
> --- a/gdb/tui/tui-io.c
> +++ b/gdb/tui/tui-io.c
> @@ -690,7 +690,7 @@ tui_expand_tabs (const char *string, int col)
>    ret = q = xmalloc (strlen (string) + n_adjust + 1);
>  
>    /* 2. Copy the original string while replacing TABs with spaces.
> */
> -  for (s = string; s; )
> +  for (col = 0, s = string; s; )
>      {
>        char *s1 = strpbrk (s, "\t");
>        if (s1)