hex2bin: fix access beyond string end

commit e4d8a29997731b3bb14059024b24df9f784288d0 upstream.

If we pass too short string to "hex2bin" (and the string size without
the terminating NUL character is even), "hex2bin" reads one byte after
the terminating NUL character.  This patch fixes it.

Note that hex_to_bin returns -1 on error and hex2bin return -EINVAL on
error - so we can't just return the variable "hi" or "lo" on error.
This inconsistency may be fixed in the next merge window, but for the
purpose of fixing this bug, we just preserve the existing behavior and
return -1 and -EINVAL.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Fixes: b78049831ffe ("lib: add error checking to hex2bin")
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/lib/hexdump.c b/lib/hexdump.c
index 0a21081acb09d8e5f8e0bb2ee66fd94f92b6d6df..c0a08ddcf94e2ee42eaf94c50727a8024464ceed 100644 (file)
--- a/lib/hexdump.c
+++ b/lib/hexdump.c
@@ -62,10 +62,13 @@ EXPORT_SYMBOL(hex_to_bin);
 int hex2bin(u8 *dst, const char *src, size_t count)
 {
        while (count--) {
-               int hi = hex_to_bin(*src++);
-               int lo = hex_to_bin(*src++);
+               int hi, lo;
 
-               if ((hi < 0) || (lo < 0))
+               hi = hex_to_bin(*src++);
+               if (unlikely(hi < 0))
+                       return -EINVAL;
+               lo = hex_to_bin(*src++);
+               if (unlikely(lo < 0))
                        return -EINVAL;
 
                *dst++ = (hi << 4) | lo;