On Thu, 2015-01-29 at 11:03 +0100, Rasmus Villemoes wrote:
> The helper hex_string() is broken in two ways. First, it doesn't
> increment buf regardless of whether there is room to print, so callers
> such as kasprintf() that try to probe the correct storage to allocate
> will get a too small return value. But even worse, kasprintf() (and
> likely anyone else trying to find the size of the result) pass NULL
> for buf and 0 for size, so we also have end == NULL. But this means
> that the end-1 in hex_string() is (char*)-1, so buf < end-1 is true
> and we get a NULL pointer deref. I double-checked this with a trivial
> kernel module that just did a kasprintf(GFP_KERNEL, "%14ph",
> "CrashBoomBang").
>
> Nobody seems to be using %ph with kasprintf, but we might as well fix
> it before it hits someone.
>
> Signed-off-by: Rasmus Villemoes <li...@rasmusvillemoes.dk>
Acked-by: Andy Shevchenko <andriy.shevche...@linux.intel.com>
> ---
> lib/vsprintf.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index ec337f64f52d..3568e3906777 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -782,11 +782,19 @@ char *hex_string(char *buf, char *end, u8 *addr, struct
> printf_spec spec,
> if (spec.field_width > 0)
> len = min_t(int, spec.field_width, 64);
>
> - for (i = 0; i < len && buf < end - 1; i++) {
> - buf = hex_byte_pack(buf, addr[i]);
> + for (i = 0; i < len; ++i) {
> + if (buf < end)
> + *buf = hex_asc_hi(addr[i]);
> + ++buf;
> + if (buf < end)
> + *buf = hex_asc_lo(addr[i]);
> + ++buf;
>
> - if (buf < end && separator && i != len - 1)
> - *buf++ = separator;
> + if (separator && i != len - 1) {
> + if (buf < end)
> + *buf = separator;
> + ++buf;
> + }
> }
>
> return buf;
--
Andy Shevchenko <andriy.shevche...@linux.intel.com>
Intel Finland Oy
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