Re: [PATCH] nl802154: Fix type check in nl802154_new_interface()

Hi,

On Mon, 12 Jul 2021 at 09:49, YueHaibing [off-list ref] wrote:

We got this UBSAN warning:

UBSAN: shift-out-of-bounds in net/ieee802154/nl802154.c:920:44
shift exponent -1 is negative
CPU: 3 PID: 8258 Comm: repro Not tainted 5.13.0+ #222
Call Trace:
 dump_stack_lvl+0x8d/0xcf
 ubsan_epilogue+0xa/0x4e
 __ubsan_handle_shift_out_of_bounds+0x161/0x182
 nl802154_new_interface+0x3bf/0x3d0
 genl_family_rcv_msg_doit.isra.15+0x12d/0x170
 genl_rcv_msg+0x11a/0x240
 netlink_rcv_skb+0x69/0x160
 genl_rcv+0x24/0x40

NL802154_IFTYPE_UNSPEC is -1, so enum nl802154_iftype type now
is a signed integer, which is assigned by nla_get_u32 in
nl802154_new_interface(), this may cause type is negative and trigger
this warning.

I think this is not the right fix, the fix is to change the UAPI that
NL802154_IFTYPE_UNSPEC fits into the netlink range of U32. I will
prepare a fix for that, it should still be backwards compatible.

- Alex