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BUG: KMSAN: uninit-value in slhc_compress+0x2c5/0x2fb0 drivers/net/slip/slhc.c:251
CPU: 0 PID: 20523 Comm: syz-executor.0 Not tainted 5.8.0-rc5-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:121
 __msan_warning+0x58/0xa0 mm/kmsan/kmsan_instr.c:215
 slhc_compress+0x2c5/0x2fb0 drivers/net/slip/slhc.c:251
 ppp_send_frame drivers/net/ppp/ppp_generic.c:1639 [inline]
 __ppp_xmit_process+0x1902/0x2970 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:737 [inline]
 do_iter_write+0xa0a/0xdc0 fs/read_write.c:1020
 compat_writev+0x2df/0x5a0 fs/read_write.c:1371
 do_compat_pwritev64 fs/read_write.c:1420 [inline]
 __do_compat_sys_pwritev fs/read_write.c:1440 [inline]
 __se_compat_sys_pwritev+0x2bd/0x370 fs/read_write.c:1434
 __ia32_compat_sys_pwritev+0x62/0x80 fs/read_write.c:1434
 do_syscall_32_irqs_on arch/x86/entry/common.c:430 [inline]
 __do_fast_syscall_32+0x2aa/0x400 arch/x86/entry/common.c:477
 do_fast_syscall_32+0x6b/0xd0 arch/x86/entry/common.c:505
 do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:554
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7fcb549
Code: Bad RIP value.
RSP: 002b:00000000f5da50cc EFLAGS: 00000296 ORIG_RAX: 000000000000014e
RAX: ffffffffffffffda RBX: 0000000000000007 RCX: 0000000020000280
RDX: 000000000000005d RSI: 0000000000000002 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

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:80
 slab_alloc_node mm/slub.c:2839 [inline]
 __kmalloc_node_track_caller+0xb40/0x1200 mm/slub.c:4478
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0x2fd/0xac0 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1083 [inline]
 ppp_write+0x115/0x790 drivers/net/ppp/ppp_generic.c:500
 do_loop_readv_writev fs/read_write.c:737 [inline]
 do_iter_write+0xa0a/0xdc0 fs/read_write.c:1020
 compat_writev+0x2df/0x5a0 fs/read_write.c:1371
 do_compat_pwritev64 fs/read_write.c:1420 [inline]
 __do_compat_sys_pwritev fs/read_write.c:1440 [inline]
 __se_compat_sys_pwritev+0x2bd/0x370 fs/read_write.c:1434
 __ia32_compat_sys_pwritev+0x62/0x80 fs/read_write.c:1434
 do_syscall_32_irqs_on arch/x86/entry/common.c:430 [inline]
 __do_fast_syscall_32+0x2aa/0x400 arch/x86/entry/common.c:477
 do_fast_syscall_32+0x6b/0xd0 arch/x86/entry/common.c:505
 do_SYSENTER_32+0x73/0x90 arch/x86/entry/common.c:554
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
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