[syzbot] [ppp?] KMSAN: uninit-value in ppp_async_push (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 614da38e2f7a Merge tag 'hid-for-linus-2024051401' of git:/..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1315203c980000
kernel config: https://syzkaller.appspot.com/x/.config?x=f5d2cbf33633f507
dashboard link: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf
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=14b284e8980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1653d768980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/89eafb874b71/disk-614da38e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/356000512ad9/vmlinux-614da38e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/839c73939115/bzImage-614da38e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ec0723...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in ppp_async_encode drivers/net/ppp/ppp_async.c:548 [inline]
BUG: KMSAN: uninit-value in ppp_async_push+0xc05/0x2660 drivers/net/ppp/ppp_async.c:675
ppp_async_encode drivers/net/ppp/ppp_async.c:548 [inline]
ppp_async_push+0xc05/0x2660 drivers/net/ppp/ppp_async.c:675
ppp_async_send+0x130/0x1b0 drivers/net/ppp/ppp_async.c:634
ppp_push+0x220/0x22b0 drivers/net/ppp/ppp_generic.c:1883
ppp_send_frame drivers/net/ppp/ppp_generic.c:1846 [inline]
__ppp_xmit_process+0x123a/0x2780 drivers/net/ppp/ppp_generic.c:1646
ppp_xmit_process+0x100/0x2b0 drivers/net/ppp/ppp_generic.c:1667
ppp_write+0x63a/0x7d0 drivers/net/ppp/ppp_generic.c:521
do_loop_readv_writev fs/read_write.c:764 [inline]
vfs_writev+0xb0e/0x1450 fs/read_write.c:973
do_pwritev fs/read_write.c:1072 [inline]
__do_sys_pwritev fs/read_write.c:1119 [inline]
__se_sys_pwritev fs/read_write.c:1114 [inline]
__x64_sys_pwritev+0x2e5/0x500 fs/read_write.c:1114
x64_sys_call+0x3539/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:297
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcf/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:3877 [inline]
slab_alloc_node mm/slub.c:3918 [inline]
kmem_cache_alloc_node+0x622/0xc90 mm/slub.c:3961
kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577
__alloc_skb+0x35b/0x7a0 net/core/skbuff.c:668
alloc_skb include/linux/skbuff.h:1319 [inline]
ppp_write+0xe5/0x7d0 drivers/net/ppp/ppp_generic.c:509
do_loop_readv_writev fs/read_write.c:764 [inline]
vfs_writev+0xb0e/0x1450 fs/read_write.c:973
do_pwritev fs/read_write.c:1072 [inline]
__do_sys_pwritev fs/read_write.c:1119 [inline]
__se_sys_pwritev fs/read_write.c:1114 [inline]
__x64_sys_pwritev+0x2e5/0x500 fs/read_write.c:1114
x64_sys_call+0x3539/0x3b50 arch/x86/include/generated/asm/syscalls_64.h:297
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 PID: 5049 Comm: syz-executor420 Not tainted 6.9.0-syzkaller-02707-g614da38e2f7a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
=====================================================


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