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BUG: KMSAN: uninit-value in slhc_compress+0x5b9/0x2e60 drivers/net/slip/slhc.c:270
CPU: 0 PID: 26923 Comm: syz-executor.2 Not tainted 5.6.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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
 slhc_compress+0x5b9/0x2e60 drivers/net/slip/slhc.c:270
 ppp_send_frame drivers/net/ppp/ppp_generic.c:1637 [inline]
 __ppp_xmit_process+0x1902/0x2970 drivers/net/ppp/ppp_generic.c:1495
 ppp_xmit_process+0x147/0x2f0 drivers/net/ppp/ppp_generic.c:1516
 ppp_write+0x6bb/0x790 drivers/net/ppp/ppp_generic.c:512
 do_loop_readv_writev fs/read_write.c:717 [inline]
 do_iter_write+0x812/0xdc0 fs/read_write.c:1000
 vfs_writev fs/read_write.c:1071 [inline]
 do_pwritev+0x487/0x7d0 fs/read_write.c:1168
 __do_sys_pwritev fs/read_write.c:1215 [inline]
 __se_sys_pwritev+0xc6/0xe0 fs/read_write.c:1210
 __x64_sys_pwritev+0x62/0x80 fs/read_write.c:1210
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45c479
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9415498c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
RAX: ffffffffffffffda RBX: 00007f94154996d4 RCX: 000000000045c479
RDX: 0000000000000001 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 000000000076bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000086e R14: 00000000004cae9c R15: 000000000076bf2c

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:144 [inline]
 kmsan_internal_poison_shadow+0x66/0xd0 mm/kmsan/kmsan.c:127
 kmsan_slab_alloc+0x8a/0xe0 mm/kmsan/kmsan_hooks.c:82
 slab_alloc_node mm/slub.c:2793 [inline]
 __kmalloc_node_track_caller+0xb40/0x1200 mm/slub.c:4401
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0x2fd/0xac0 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1051 [inline]
 ppp_write+0x115/0x790 drivers/net/ppp/ppp_generic.c:500
 do_loop_readv_writev fs/read_write.c:717 [inline]
 do_iter_write+0x812/0xdc0 fs/read_write.c:1000
 vfs_writev fs/read_write.c:1071 [inline]
 do_pwritev+0x487/0x7d0 fs/read_write.c:1168
 __do_sys_pwritev fs/read_write.c:1215 [inline]
 __se_sys_pwritev+0xc6/0xe0 fs/read_write.c:1210
 __x64_sys_pwritev+0x62/0x80 fs/read_write.c:1210
 do_syscall_64+0xb8/0x160 arch/x86/entry/common.c:296
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
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