On Fri, Feb 23, 2018 at 09:17:48PM +0100, Stefan Hellermann wrote:
Commit 4904dbda41c8 ("ARM: orion5x: use mac_pton() helper") crashes my QNAP TS-209 NAS early on boot.
The boot code for the TS-209 is looping through an ext2 filesystem on a 384kB mtd partition (factory configuration put there by QNAP). There it looks on every 1kB boundary if there is a valid MAC address. The filesystem has a 1kB block size, so this seems to work.
On my device the MAC address is on the 37th 1kB block. But: On the 27th block is a large file (1,5kB) without 0 bytes inside. The code in qnap_tsx09_find_mac_addr() maps 1kB into memory (not a whole file or the whole 384kB) and then calls qnap_tsx09_check_mac_addr() -> mac_pton() -> strlen() on this memory block. as there is no 0 byte in the file on the 27th block, strlen() runs into bad memory and the machine panics. The old code had no strlen().
Actually mac_pton() doesn't need to call strlen(), the following loop catches short strings quite nicely. The strlen() seems to be an optimization for calls to mac_pton with empty string. But this is rarely the case and this is not a hot path. Remove it to reduce code size and speed up calls with an not empty string.
Besides fixing the crash there is are other users interested in this change, see https://patchwork.ozlabs.org/patch/851008/
Fixes: 4904dbda41c8 ("ARM: orion5x: use mac_pton() helper") Signed-off-by: Stefan Hellermann stefan@the2masters.de Cc: stable@vger.kernel.org [4.4+]
Reviewed-by: Andrew Lunn andrew@lunn.ch
Andrew