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BUG: KMSAN: uninit-value in slhc_compress+0x2c8/0x2f60 drivers/net/slip/slhc.c:251
CPU: 1 PID: 10145 Comm: syz-executor.0 Not tainted 5.10.0-rc1-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+0x1df/0x240 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
 __msan_warning+0x5f/0xa0 mm/kmsan/kmsan_instr.c:197
 slhc_compress+0x2c8/0x2f60 drivers/net/slip/slhc.c:251
 ppp_send_frame drivers/net/ppp/ppp_generic.c:1639 [inline]
 __ppp_xmit_process+0x126b/0x2900 drivers/net/ppp/ppp_generic.c:1497
 ppp_xmit_process+0x147/0x2f0 drivers/net/ppp/ppp_generic.c:1518
 ppp_write+0x6bb/0x790 drivers/net/ppp/ppp_generic.c:512
 do_loop_readv_writev fs/read_write.c:764 [inline]
 do_iter_write+0xa61/0xe20 fs/read_write.c:868
 vfs_writev fs/read_write.c:939 [inline]
 do_pwritev+0x487/0x7d0 fs/read_write.c:1036
 __do_sys_pwritev fs/read_write.c:1083 [inline]
 __se_sys_pwritev+0xc6/0xe0 fs/read_write.c:1078
 __x64_sys_pwritev+0x62/0x80 fs/read_write.c:1078
 do_syscall_64+0xa2/0x120 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cae9
Code: 8d 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 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f6909fdcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000128
RAX: ffffffffffffffda RBX: 00000000004fad40 RCX: 000000000045cae9
RDX: 0000000000000003 RSI: 0000000020000480 RDI: 0000000000000003
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000879 R14: 00000000004cb60e R15: 00007f6909fdd6d4

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:121 [inline]
 kmsan_internal_poison_shadow+0x5c/0xf0 mm/kmsan/kmsan.c:104
 kmsan_slab_alloc+0x8d/0xe0 mm/kmsan/kmsan_hooks.c:76
 slab_alloc_node mm/slub.c:2906 [inline]
 __kmalloc_node_track_caller+0x98e/0x1740 mm/slub.c:4512
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0x2d8/0xa90 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1094 [inline]
 ppp_write+0x115/0x790 drivers/net/ppp/ppp_generic.c:500
 do_loop_readv_writev fs/read_write.c:764 [inline]
 do_iter_write+0xa61/0xe20 fs/read_write.c:868
 vfs_writev fs/read_write.c:939 [inline]
 do_pwritev+0x487/0x7d0 fs/read_write.c:1036
 __do_sys_pwritev fs/read_write.c:1083 [inline]
 __se_sys_pwritev+0xc6/0xe0 fs/read_write.c:1078
 __x64_sys_pwritev+0x62/0x80 fs/read_write.c:1078
 do_syscall_64+0xa2/0x120 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
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