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BUG: KASAN: use-after-free in slc_sync drivers/net/can/slcan.c:504 [inline]
BUG: KASAN: use-after-free in slcan_open+0x847/0xa50 drivers/net/can/slcan.c:579
Read of size 8 at addr ffff88807ef50b48 by task syz-executor.5/7845

CPU: 0 PID: 7845 Comm: syz-executor.5 Not tainted 5.4.0-rc7-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+0x12d/0x187 lib/dump_stack.c:118
 print_address_description.constprop.8.cold.10+0x9/0x31d mm/kasan/report.c:374
 __kasan_report.cold.11+0x1b/0x3a 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
 slc_sync drivers/net/can/slcan.c:504 [inline]
 slcan_open+0x847/0xa50 drivers/net/can/slcan.c:579
 tty_ldisc_open.isra.3+0x78/0xc0 drivers/tty/tty_ldisc.c:469
 tty_set_ldisc+0x238/0x5b0 drivers/tty/tty_ldisc.c:596
 tiocsetd drivers/tty/tty_io.c:2334 [inline]
 tty_ioctl+0x332/0x12f0 drivers/tty/tty_io.c:2594
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x196/0x1150 fs/ioctl.c:696
 ksys_ioctl+0x62/0x90 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718
 do_syscall_64+0xca/0x5d0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a679
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:00007f54e1429c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f54e1429c90 RCX: 000000000045a679
RDX: 00000000200000c0 RSI: 0000000000005423 RDI: 0000000000000004
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f54e142a6d4
R13: 00000000004c5310 R14: 00000000004da8b0 R15: 0000000000000005

Allocated by task 7860:
 save_stack+0x21/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc.constprop.13+0xc7/0xd0 mm/kasan/common.c:510
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
 __do_kmalloc_node mm/slab.c:3615 [inline]
 __kmalloc_node+0x4d/0x70 mm/slab.c:3622
 kmalloc_node include/linux/slab.h:599 [inline]
 kvmalloc_node+0x40/0x80 mm/util.c:564
 kvmalloc include/linux/mm.h:670 [inline]
 kvzalloc include/linux/mm.h:678 [inline]
 alloc_netdev_mqs+0x5d/0xca0 net/core/dev.c:9730
 slc_alloc drivers/net/can/slcan.c:533 [inline]
 slcan_open+0x301/0xa50 drivers/net/can/slcan.c:590
 tty_ldisc_open.isra.3+0x78/0xc0 drivers/tty/tty_ldisc.c:469
 tty_set_ldisc+0x238/0x5b0 drivers/tty/tty_ldisc.c:596
 tiocsetd drivers/tty/tty_io.c:2334 [inline]
 tty_ioctl+0x332/0x12f0 drivers/tty/tty_io.c:2594
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x196/0x1150 fs/ioctl.c:696
 ksys_ioctl+0x62/0x90 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718
 do_syscall_64+0xca/0x5d0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7860:
 save_stack+0x21/0x90 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+0x108/0x2c0 mm/slab.c:3756
 kvfree+0x2c/0x30 mm/util.c:593
 netdev_freemem net/core/dev.c:9684 [inline]
 free_netdev+0x342/0x400 net/core/dev.c:9839
 slcan_open+0x790/0xa50 drivers/net/can/slcan.c:620
 tty_ldisc_open.isra.3+0x78/0xc0 drivers/tty/tty_ldisc.c:469
 tty_set_ldisc+0x238/0x5b0 drivers/tty/tty_ldisc.c:596
 tiocsetd drivers/tty/tty_io.c:2334 [inline]
 tty_ioctl+0x332/0x12f0 drivers/tty/tty_io.c:2594
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x196/0x1150 fs/ioctl.c:696
 ksys_ioctl+0x62/0x90 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718
 do_syscall_64+0xca/0x5d0 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88807ef50000
 which belongs to the cache kmalloc-32k of size 32768
The buggy address is located 2888 bytes inside of
 32768-byte region [ffff88807ef50000, ffff88807ef58000)
The buggy address belongs to the page:
page:ffffea0001fbd400 refcount:1 mapcount:0 mapping:ffff8880aa402540 index:0x0 compound_mapcount: 0
raw: 00fffe0000010200 ffffea0001fbd808 ffff8880aa401d48 ffff8880aa402540
raw: 0000000000000000 ffff88807ef50000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88807ef50a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807ef50a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807ef50b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff88807ef50b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807ef50c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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