=====================================================
BUG: KMSAN: uninit-value in slhc_compress+0x306/0x3c50 drivers/net/slip/slhc.c:251
 slhc_compress+0x306/0x3c50 drivers/net/slip/slhc.c:251
 ppp_send_frame+0x14f4/0x27c0 drivers/net/ppp/ppp_generic.c:1782
 __ppp_xmit_process+0x23e/0x4b0 drivers/net/ppp/ppp_generic.c:1640
 ppp_xmit_process+0x1fe/0x480 drivers/net/ppp/ppp_generic.c:1661
 ppp_write+0x5cb/0x5e0 drivers/net/ppp/ppp_generic.c:513
 do_iter_write+0xb0c/0x1500 fs/read_write.c:853
 vfs_writev fs/read_write.c:924 [inline]
 do_pwritev+0x647/0xc60 fs/read_write.c:1021
 __do_sys_pwritev fs/read_write.c:1068 [inline]
 __se_sys_pwritev fs/read_write.c:1063 [inline]
 __x64_sys_pwritev+0x120/0x170 fs/read_write.c:1063
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was created at:
 slab_post_alloc_hook mm/slab.h:524 [inline]
 slab_alloc_node mm/slub.c:3251 [inline]
 __kmalloc_node_track_caller+0xe0c/0x1510 mm/slub.c:4974
 kmalloc_reserve net/core/skbuff.c:354 [inline]
 __alloc_skb+0x545/0xf90 net/core/skbuff.c:426
 alloc_skb include/linux/skbuff.h:1126 [inline]
 ppp_write+0x11d/0x5e0 drivers/net/ppp/ppp_generic.c:501
 do_iter_write+0xb0c/0x1500 fs/read_write.c:853
 vfs_writev fs/read_write.c:924 [inline]
 do_pwritev+0x647/0xc60 fs/read_write.c:1021
 __do_sys_pwritev fs/read_write.c:1068 [inline]
 __se_sys_pwritev fs/read_write.c:1063 [inline]
 __x64_sys_pwritev+0x120/0x170 fs/read_write.c:1063
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

CPU: 0 PID: 9386 Comm: syz-executor.3 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
=====================================================