[PATCH] mac802154: Fix uninit-value access in ieee802154_hdr_push_sechdr

The syzkaller reported an issue:

BUG: KMSAN: uninit-value in ieee802154_hdr_push_sechdr net/ieee802154/header_ops.c:54 [inline]
BUG: KMSAN: uninit-value in ieee802154_hdr_push+0x971/0xb90 net/ieee802154/header_ops.c:108
 ieee802154_hdr_push_sechdr net/ieee802154/header_ops.c:54 [inline]
 ieee802154_hdr_push+0x971/0xb90 net/ieee802154/header_ops.c:108
 ieee802154_header_create+0x9c0/0xc00 net/mac802154/iface.c:396
 wpan_dev_hard_header include/net/cfg802154.h:494 [inline]
 dgram_sendmsg+0xd1d/0x1500 net/ieee802154/socket.c:677
 ieee802154_sock_sendmsg+0x91/0xc0 net/ieee802154/socket.c:96
 sock_sendmsg_nosec net/socket.c:725 [inline]
 sock_sendmsg net/socket.c:748 [inline]
 ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2494
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2548
 __sys_sendmsg+0x225/0x3c0 net/socket.c:2577
 __compat_sys_sendmsg net/compat.c:346 [inline]
 __do_compat_sys_sendmsg net/compat.c:353 [inline]
 __se_compat_sys_sendmsg net/compat.c:350 [inline]

We found hdr->key_id_mode is uninitialized in mac802154_set_header_security()
which indicates hdr.fc.security_enabled should be 0. However, it is set to be cb->secen before.
Later, ieee802154_hdr_push_sechdr is invoked, causing KMSAN complains uninit-value issue.
Since mac802154_set_header_security() sets hdr.fc.security_enabled based on the variables
ieee802154_sub_if_data *sdata and ieee802154_mac_cb *cb in a collaborative manner.
Therefore, we should not set security_enabled prior to mac802154_set_header_security().

Fixed it by removing the line that sets the hdr.fc.security_enabled.

Syzkaller don't provide repro, and I provide a syz repro like:
r0 = syz_init_net_socket$802154_dgram(0x24, 0x2, 0x0)
setsockopt$WPAN_SECURITY(r0, 0x0, 0x1, &(0x7f0000000000)=0x2, 0x4)
setsockopt$WPAN_SECURITY(r0, 0x0, 0x1, &(0x7f0000000080), 0x4)
sendmsg$802154_dgram(r0, &(0x7f0000000100)={&(0x7f0000000040)={0x24, @short}, 0x14, &(0x7f00000000c0)={0x0}}, 0x0)

Fixes: 32edc40ae65c ("ieee802154: change _cb handling slightly")
Signed-off-by: Zhang Shurong <redacted>
---
 net/mac802154/iface.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/mac802154/iface.c b/net/mac802154/iface.c
index c0e2da5072be..c99b6e40a5db 100644
--- a/net/mac802154/iface.c
+++ b/net/mac802154/iface.c

@@ -368,7 +368,6 @@ static int ieee802154_header_create(struct sk_buff *skb,
 
 	memset(&hdr.fc, 0, sizeof(hdr.fc));
 	hdr.fc.type = cb->type;
-	hdr.fc.security_enabled = cb->secen;
 	hdr.fc.ack_request = cb->ackreq;
 	hdr.seq = atomic_inc_return(&dev->ieee802154_ptr->dsn) & 0xFF;
 

-- 
2.30.2