ieee802154: fix kernel-infoleak in dgram_recvmsg()

ieee802154: fix kernel-infoleak in dgram_recvmsg()

KMSAN reported a kernel-infoleak in move_addr_to_user():

BUG: KMSAN: kernel-infoleak in instrument_copy_to_user
include/linux/instrumented.h:131 [inline]
BUG: KMSAN: kernel-infoleak in _inline_copy_to_user
include/linux/uaccess.h:205 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_user+0xcc/0x120
lib/usercopy.c:26
 instrument_copy_to_user include/linux/instrumented.h:131 [inline]
 _inline_copy_to_user include/linux/uaccess.h:205 [inline]
 _copy_to_user+0xcc/0x120 lib/usercopy.c:26
 copy_to_user include/linux/uaccess.h:236 [inline]
 move_addr_to_user+0x2e7/0x440 net/socket.c:302
 ____sys_recvmsg+0x232/0x610 net/socket.c:2925
 ...
 Uninit was stored to memory at:
 ieee802154_addr_to_sa include/net/ieee802154_netdev.h:369 [inline]
 dgram_recvmsg+0xa09/0xbe0 net/ieee802154/socket.c:739

The issue occurs because the `pan_id` field of `struct ieee802154_addr`
is left uninitialized when the address mode is `IEEE802154_ADDR_NONE`.
The execution flow is as follows:

1. `__ieee802154_rx_handle_packet()` declares a local `struct
ieee802154_hdr hdr` on the stack.
2. `ieee802154_hdr_pull()` calls `ieee802154_hdr_get_addr()` to parse
the source and destination addresses into this structure.
3. If the address mode is `IEEE802154_ADDR_NONE`,
`ieee802154_hdr_get_addr()` previously only set the `mode` field,
leaving the `pan_id` field containing uninitialized stack memory.
4. This uninitialized `pan_id` is later copied into a `struct
sockaddr_ieee802154` in `dgram_recvmsg()` via `ieee802154_addr_to_sa()`.
5. Finally, `move_addr_to_user()` copies the socket address structure to
user space, leaking the uninitialized bytes.

Fix this by using `memset` to zero out the address structure in
`ieee802154_hdr_get_addr()` when the mode is `IEEE802154_ADDR_NONE`.

Fixes: 94b4f6c21cf5 ("ieee802154: add header structs with endiannes and operations")
Assisted-by: Gemini:gemini-3.1-pro-preview Gemini:gemini-3-flash-preview syzbot
Reported-by: syzbot+346474e3bf0b26bd3090@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=346474e3bf0b26bd3090
Link: https://syzkaller.appspot.com/ai_job?id=a507a109-d683-4a2c-bc03-93394f491b17
Signed-off-by: Aleksandr Nogikh <nogikh@google.com>
Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/62795fd9-fc0c-48eb-bb82-05ffc5a57104@mail.kernel.org
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>