[syzbot] [net?] KMSAN: uninit-value in slhc_remember

[syzbot] [net?] KMSAN: uninit-value in slhc_remember

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    5b7c893ed5ed Merge tag 'ntfs3_for_6.12' of https://github...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=131de327980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=981fe2ff8a1e457a
dashboard link: https://syzkaller.appspot.com/bug?extid=2ada1bc857496353be5a
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/6bb953eff17f/disk-5b7c893e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0e63ae322aa8/vmlinux-5b7c893e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a0ed59d4302c/bzImage-5b7c893e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2ada1bc857496353be5a@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in slhc_remember+0x2e8/0x7b0 drivers/net/slip/slhc.c:666
 slhc_remember+0x2e8/0x7b0 drivers/net/slip/slhc.c:666
 ppp_receive_nonmp_frame+0xe45/0x35e0 drivers/net/ppp/ppp_generic.c:2455
 ppp_receive_frame drivers/net/ppp/ppp_generic.c:2372 [inline]
 ppp_do_recv+0x65f/0x40d0 drivers/net/ppp/ppp_generic.c:2212
 ppp_input+0x7dc/0xe60 drivers/net/ppp/ppp_generic.c:2327
 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:729 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:744
 ____sys_sendmsg+0x903/0xb60 net/socket.c:2602
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2656
 __sys_sendmmsg+0x3c1/0x960 net/socket.c:2742
 __do_sys_sendmmsg net/socket.c:2771 [inline]
 __se_sys_sendmmsg net/socket.c:2768 [inline]
 __x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2768
 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:4091 [inline]
 slab_alloc_node mm/slub.c:4134 [inline]
 kmem_cache_alloc_node_noprof+0x6bf/0xb80 mm/slub.c:4186
 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:729 [inline]
 __sock_sendmsg+0x30f/0x380 net/socket.c:744
 ____sys_sendmsg+0x903/0xb60 net/socket.c:2602
 ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2656
 __sys_sendmmsg+0x3c1/0x960 net/socket.c:2742
 __do_sys_sendmmsg net/socket.c:2771 [inline]
 __se_sys_sendmmsg net/socket.c:2768 [inline]
 __x64_sys_sendmmsg+0xbc/0x120 net/socket.c:2768
 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: 11151 Comm: syz.3.1054 Not tainted 6.12.0-rc2-syzkaller-00050-g5b7c893ed5ed #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
=====================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup