net: fix uninit-value in caif_seqpkt_sendmsg

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: net: fix uninit-value in caif_seqpkt_sendmsg When nr_segs equal to zero in iovec_from_user, the object msg->msg_iter.iov is uninit stack memory in caif_seqpkt_sendmsg which is defined in ___sys_sendmsg. So we cann't just judge msg->msg_iter.iov->base directlly. We can use nr_segs to judge msg in caif_seqpkt_sendmsg whether has data buffers. ===================================================== BUG: KMSAN: uninit-value in caif_seqpkt_sendmsg+0x693/0xf60 net/caif/caif_socket.c:542 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1c9/0x220 lib/dump_stack.c:118 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215 caif_seqpkt_sendmsg+0x693/0xf60 net/caif/caif_socket.c:542 sock_sendmsg_nosec net/socket.c:652 [inline] sock_sendmsg net/socket.c:672 [inline] ____sys_sendmsg+0x12b6/0x1350 net/socket.c:2343 ___sys_sendmsg net/socket.c:2397 [inline] __sys_sendmmsg+0x808/0xc90 net/socket.c:2480 __compat_sys_sendmmsg net/compat.c:656 [inline]

References

• https://git.kernel.org/stable/c/d9d646acad2c3590e189bb5d5c86ab8bd8a2dfc3
• https://git.kernel.org/stable/c/5c6d8e2f7187b8e45a18c27acb7a3885f03ee3db
• https://git.kernel.org/stable/c/ffe31dd70b70a40cd6b21b78c1713a23e021843a
• https://git.kernel.org/stable/c/452c3ed7bf63721b07bc2238ed1261bb26027e85
• https://git.kernel.org/stable/c/9413c0abb57f70a953b1116318d6aa478013c35d
• https://git.kernel.org/stable/c/1582a02fecffcee306663035a295e28e1c4aaaff
• https://git.kernel.org/stable/c/d4c7797ab1517515f0d08b3bc1c6b48883889c54
• https://git.kernel.org/stable/c/991e634360f2622a683b48dfe44fe6d9cb765a09