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BUG: KASAN: use-after-free in sl_sync drivers/net/slip/slip.c:725 [inline]
BUG: KASAN: use-after-free in slip_open+0xecd/0x11b7 drivers/net/slip/slip.c:801
Read of size 8 at addr ffff888044cc0b48 by task syz-executor.4/28702

CPU: 1 PID: 28702 Comm: syz-executor.4 Not tainted 5.4.0-rc8-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+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:634
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 sl_sync drivers/net/slip/slip.c:725 [inline]
 slip_open+0xecd/0x11b7 drivers/net/slip/slip.c:801
 tty_ldisc_open.isra.0+0xa3/0x110 drivers/tty/tty_ldisc.c:469
 tty_set_ldisc+0x30e/0x6b0 drivers/tty/tty_ldisc.c:596
 tiocsetd drivers/tty/tty_io.c:2334 [inline]
 tty_ioctl+0xe8d/0x14f0 drivers/tty/tty_io.c:2594
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a639
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:00007f1598efec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a639
RDX: 0000000020000000 RSI: 0000000000005423 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f1598eff6d4
R13: 00000000004c52d0 R14: 00000000004da3f0 R15: 00000000ffffffff

Allocated by task 28701:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc mm/kasan/common.c:510 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
 __do_kmalloc_node mm/slab.c:3615 [inline]
 __kmalloc_node+0x4e/0x70 mm/slab.c:3622
 kmalloc_node include/linux/slab.h:599 [inline]
 kvmalloc_node+0x68/0x100 mm/util.c:564
 kvmalloc include/linux/mm.h:670 [inline]
 kvzalloc include/linux/mm.h:678 [inline]
 alloc_netdev_mqs+0x98/0xde0 net/core/dev.c:9499
 sl_alloc drivers/net/slip/slip.c:751 [inline]
 slip_open+0x38e/0x11b7 drivers/net/slip/slip.c:812
 tty_ldisc_open.isra.0+0xa3/0x110 drivers/tty/tty_ldisc.c:469
 tty_set_ldisc+0x30e/0x6b0 drivers/tty/tty_ldisc.c:596
 tiocsetd drivers/tty/tty_io.c:2334 [inline]
 tty_ioctl+0xe8d/0x14f0 drivers/tty/tty_io.c:2594
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 28701:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 kasan_set_free_info mm/kasan/common.c:332 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
 __cache_free mm/slab.c:3425 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3756
 kvfree+0x61/0x70 mm/util.c:593
 netdev_freemem net/core/dev.c:9453 [inline]
 free_netdev+0x3c0/0x470 net/core/dev.c:9608
 slip_open+0xd70/0x11b7 drivers/net/slip/slip.c:858
 tty_ldisc_open.isra.0+0xa3/0x110 drivers/tty/tty_ldisc.c:469
 tty_set_ldisc+0x30e/0x6b0 drivers/tty/tty_ldisc.c:596
 tiocsetd drivers/tty/tty_io.c:2334 [inline]
 tty_ioctl+0xe8d/0x14f0 drivers/tty/tty_io.c:2594
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0xdb6/0x13e0 fs/ioctl.c:696
 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888044cc0000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 2888 bytes inside of
 4096-byte region [ffff888044cc0000, ffff888044cc1000)
The buggy address belongs to the page:
page:ffffea0001133000 refcount:1 mapcount:0 mapping:ffff8880aa402000 index:0x0 compound_mapcount: 0
raw: 01fffc0000010200 ffffea0000a77f08 ffffea00023e4d88 ffff8880aa402000
raw: 0000000000000000 ffff888044cc0000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888044cc0a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888044cc0a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888044cc0b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888044cc0b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888044cc0c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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