[syzbot] [ppp?] KMSAN: uninit-value in ppp_async_push (4)

Hello,

syzbot found the following issue on:

HEAD commit:    1868f9d0260e Merge tag 'for-linux-6.12-ofs1' of git://git...
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13730e07980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=acaa65be5f19fc5a
dashboard link: https://syzkaller.appspot.com/bug?extid=1d121645899e7692f92a
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=127f8080580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14b86c27980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/51af83d2907b/disk-1868f9d0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4cd235c942a6/vmlinux-1868f9d0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a321106ef897/bzImage-1868f9d0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

=====================================================
BUG: KMSAN: uninit-value in ppp_async_encode drivers/net/ppp/ppp_async.c:545 [inline]
BUG: KMSAN: uninit-value in ppp_async_push+0xb4f/0x2660 drivers/net/ppp/ppp_async.c:675
 ppp_async_encode drivers/net/ppp/ppp_async.c:545 [inline]
 ppp_async_push+0xb4f/0x2660 drivers/net/ppp/ppp_async.c:675
 ppp_async_send+0x130/0x1b0 drivers/net/ppp/ppp_async.c:634
 ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2280 [inline]
 ppp_input+0x1f1/0xe60 drivers/net/ppp/ppp_generic.c:2304
 pppoe_rcv_core+0x1d3/0x720 drivers/net/ppp/pppoe.c:379
 sk_backlog_rcv+0x13b/0x420 include/net/sock.h:1113
 __release_sock+0x1da/0x330 net/core/sock.c:3072
 release_sock+0x6b/0x250 net/core/sock.c:3626
 pppoe_sendmsg+0x2b8/0xb90 drivers/net/ppp/pppoe.c:903
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:745
 ____sys_sendmsg+0x903/0xb60 net/socket.c:2603
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2657
 __sys_sendmmsg+0x3be/0x950 net/socket.c:2743
 __do_sys_sendmmsg net/socket.c:2772 [inline]
 __se_sys_sendmmsg net/socket.c:2769 [inline]
 __x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2769
 x64_sys_call+0xb6e/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4092 [inline]
 slab_alloc_node mm/slub.c:4135 [inline]
 kmem_cache_alloc_node_noprof+0x6bf/0xb80 mm/slub.c:4187
 kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:587
 __alloc_skb+0x363/0x7b0 net/core/skbuff.c:678
 alloc_skb include/linux/skbuff.h:1322 [inline]
 sock_wmalloc+0xfe/0x1a0 net/core/sock.c:2732
 pppoe_sendmsg+0x3a7/0xb90 drivers/net/ppp/pppoe.c:867
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:745
 ____sys_sendmsg+0x903/0xb60 net/socket.c:2603
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2657
 __sys_sendmmsg+0x3be/0x950 net/socket.c:2743
 __do_sys_sendmmsg net/socket.c:2772 [inline]
 __se_sys_sendmmsg net/socket.c:2769 [inline]
 __x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2769
 x64_sys_call+0xb6e/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 5200 Comm: syz-executor848 Not tainted 6.11.0-syzkaller-07462-g1868f9d0260e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
=====================================================


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