syzbot

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BUG: KMSAN: uninit-value in pptp_xmit+0xf1d/0x24e0 drivers/net/ppp/pptp.c:179
CPU: 1 PID: 6272 Comm: syz-executor.3 Not tainted 5.12.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x24c/0x2e0 lib/dump_stack.c:120
 kmsan_report+0xfb/0x1e0 mm/kmsan/kmsan_report.c:118
 __msan_warning+0x5c/0xa0 mm/kmsan/kmsan_instr.c:197
 pptp_xmit+0xf1d/0x24e0 drivers/net/ppp/pptp.c:179
 __ppp_channel_push+0x1a7/0x3b0 drivers/net/ppp/ppp_generic.c:2109
 ppp_channel_push drivers/net/ppp/ppp_generic.c:2136 [inline]
 ppp_write+0x785/0x810 drivers/net/ppp/ppp_generic.c:517
 vfs_write+0x6cc/0x1b00 fs/read_write.c:603
 ksys_write+0x275/0x500 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:667
 __x64_sys_write+0x4a/0x70 fs/read_write.c:667
 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4665d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff57db0f188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 0000000000a9fb1f R14: 00007ff57db0f300 R15: 0000000000022000

Uninit was stored to memory at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:121 [inline]
 kmsan_internal_chain_origin+0xad/0x130 mm/kmsan/kmsan.c:289
 kmsan_memcpy_memmove_metadata+0x25e/0x2d0 mm/kmsan/kmsan.c:226
 kmsan_memcpy_metadata+0xb/0x10 mm/kmsan/kmsan.c:246
 __msan_memcpy+0x46/0x60 mm/kmsan/kmsan_instr.c:110
 pskb_expand_head+0x3d6/0x1e20 net/core/skbuff.c:1685
 skb_realloc_headroom+0x1af/0x310 net/core/skbuff.c:1758
 pptp_xmit+0x9a4/0x24e0 drivers/net/ppp/pptp.c:167
 __ppp_channel_push+0x1a7/0x3b0 drivers/net/ppp/ppp_generic.c:2109
 ppp_channel_push drivers/net/ppp/ppp_generic.c:2136 [inline]
 ppp_write+0x785/0x810 drivers/net/ppp/ppp_generic.c:517
 vfs_write+0x6cc/0x1b00 fs/read_write.c:603
 ksys_write+0x275/0x500 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:667
 __x64_sys_write+0x4a/0x70 fs/read_write.c:667
 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xae

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+0x8e/0xe0 mm/kmsan/kmsan_hooks.c:76
 slab_alloc_node mm/slub.c:2922 [inline]
 __kmalloc_node_track_caller+0xa4f/0x1470 mm/slub.c:4609
 kmalloc_reserve net/core/skbuff.c:353 [inline]
 __alloc_skb+0x4dd/0xe90 net/core/skbuff.c:424
 alloc_skb include/linux/skbuff.h:1103 [inline]
 ppp_write+0x11f/0x810 drivers/net/ppp/ppp_generic.c:501
 vfs_write+0x6cc/0x1b00 fs/read_write.c:603
 ksys_write+0x275/0x500 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write+0x92/0xb0 fs/read_write.c:667
 __x64_sys_write+0x4a/0x70 fs/read_write.c:667
 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xae
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