[syzbot] [serial?] KASAN: slab-use-after-free Read in tty_write_room (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0802e17d9aca Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=122e60b3e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=f9616b7e180577ba
dashboard link: https://syzkaller.appspot.com/bug?extid=2a81fdd5c6ddffee3894
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e84e45f27a78/disk-0802e17d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a8b16d2fc3b1/vmlinux-0802e17d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4c7ac36b3de1/Image-0802e17d.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2a81fd...@syzkaller.appspotmail.com

ieee802154 phy0 wpan0: encryption failed: -22
ieee802154 phy1 wpan1: encryption failed: -22
==================================================================
BUG: KASAN: slab-use-after-free in tty_write_room+0x3c/0x8c drivers/tty/tty_ioctl.c:68
Read of size 8 at addr ffff00011c808020 by task aoe_tx0/2217

CPU: 1 PID: 2217 Comm: aoe_tx0 Not tainted 6.7.0-rc8-syzkaller-g0802e17d9aca #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Call trace:
dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:291
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:298
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:364 [inline]
print_report+0x174/0x514 mm/kasan/report.c:475
kasan_report+0xd8/0x138 mm/kasan/report.c:588
__asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381
tty_write_room+0x3c/0x8c drivers/tty/tty_ioctl.c:68
handle_tx+0x120/0x604 drivers/net/caif/caif_serial.c:226
caif_xmit+0x108/0x150 drivers/net/caif/caif_serial.c:282
__netdev_start_xmit include/linux/netdevice.h:4940 [inline]
netdev_start_xmit include/linux/netdevice.h:4954 [inline]
xmit_one net/core/dev.c:3548 [inline]
dev_hard_start_xmit+0x240/0x8ac net/core/dev.c:3564
__dev_queue_xmit+0x1570/0x31d8 net/core/dev.c:4349
dev_queue_xmit include/linux/netdevice.h:3134 [inline]
tx+0x90/0x134 drivers/block/aoe/aoenet.c:62
kthread+0x1ac/0x374 drivers/block/aoe/aoecmd.c:1229
kthread+0x288/0x310 kernel/kthread.c:388
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:857

Allocated by task 12667:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4c/0x7c mm/kasan/common.c:52
kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:511
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0xac/0xc4 mm/kasan/common.c:383
kasan_kmalloc include/linux/kasan.h:198 [inline]
kmalloc_trace+0x70/0x88 mm/slab_common.c:1103
kmalloc include/linux/slab.h:600 [inline]
kzalloc include/linux/slab.h:721 [inline]
alloc_tty_struct+0xb8/0x684 drivers/tty/tty_io.c:3093
tty_init_dev+0x60/0x3ec drivers/tty/tty_io.c:1411
ptmx_open+0xfc/0x2d0 drivers/tty/pty.c:824
chrdev_open+0x3c8/0x4dc fs/char_dev.c:414
do_dentry_open+0x778/0x12b4 fs/open.c:948
vfs_open+0x7c/0x90 fs/open.c:1082
do_open fs/namei.c:3622 [inline]
path_openat+0x1f6c/0x2888 fs/namei.c:3779
do_filp_open+0x1bc/0x3cc fs/namei.c:3809
do_sys_openat2+0x124/0x1b8 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__arm64_sys_openat+0x1f0/0x240 fs/open.c:1463
__invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595

Freed by task 6202:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4c/0x7c mm/kasan/common.c:52
kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:522
____kasan_slab_free+0x144/0x1c0 mm/kasan/common.c:236
__kasan_slab_free+0x18/0x28 mm/kasan/common.c:244
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1800 [inline]
slab_free_freelist_hook mm/slub.c:1826 [inline]
slab_free mm/slub.c:3809 [inline]
__kmem_cache_free+0x2ac/0x480 mm/slub.c:3822
kfree+0xb8/0x19c mm/slab_common.c:1056
free_tty_struct drivers/tty/tty_io.c:174 [inline]
release_one_tty+0x22c/0x24c drivers/tty/tty_io.c:1544
process_one_work+0x694/0x1204 kernel/workqueue.c:2627
process_scheduled_works kernel/workqueue.c:2700 [inline]
worker_thread+0x938/0xef4 kernel/workqueue.c:2781
kthread+0x288/0x310 kernel/kthread.c:388
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:857

Last potentially related work creation:
kasan_save_stack+0x40/0x6c mm/kasan/common.c:45
__kasan_record_aux_stack+0xcc/0xe8 mm/kasan/generic.c:492
kasan_record_aux_stack_noalloc+0x14/0x20 mm/kasan/generic.c:502
insert_work+0x54/0x2d4 kernel/workqueue.c:1647
__queue_work+0xcb0/0x12bc kernel/workqueue.c:1796
queue_work_on+0x9c/0x128 kernel/workqueue.c:1831
queue_work include/linux/workqueue.h:562 [inline]
schedule_work include/linux/workqueue.h:623 [inline]
queue_release_one_tty drivers/tty/tty_io.c:1555 [inline]
kref_put include/linux/kref.h:65 [inline]
tty_kref_put+0x14c/0x1c0 drivers/tty/tty_io.c:1568
release_tty+0x3f0/0x4ac drivers/tty/tty_io.c:1604
tty_release_struct+0xb4/0xd4 drivers/tty/tty_io.c:1703
tty_release+0xb64/0x1014 drivers/tty/tty_io.c:1863
__fput+0x308/0x8e4 fs/file_table.c:394
__fput_sync+0x60/0x9c fs/file_table.c:475
__do_sys_close fs/open.c:1587 [inline]
__se_sys_close fs/open.c:1572 [inline]
__arm64_sys_close+0x150/0x1e0 fs/open.c:1572
__invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
el0_svc+0x54/0x158 arch/arm64/kernel/entry-common.c:678
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595

Second to last potentially related work creation:
kasan_save_stack+0x40/0x6c mm/kasan/common.c:45
__kasan_record_aux_stack+0xcc/0xe8 mm/kasan/generic.c:492
kasan_record_aux_stack_noalloc+0x14/0x20 mm/kasan/generic.c:502
__call_rcu_common kernel/rcu/tree.c:2681 [inline]
call_rcu+0x104/0xaf4 kernel/rcu/tree.c:2795
in6_dev_finish_destroy+0x158/0x1d8 net/ipv6/addrconf_core.c:271
in6_dev_put include/net/addrconf.h:388 [inline]
addrconf_ifdown+0x152c/0x17c8 net/ipv6/addrconf.c:3960
addrconf_notify+0x340/0xcf0
notifier_call_chain+0x1a4/0x510 kernel/notifier.c:93
raw_notifier_call_chain+0x3c/0x50 kernel/notifier.c:461
call_netdevice_notifiers_info net/core/dev.c:1967 [inline]
call_netdevice_notifiers_extack net/core/dev.c:2005 [inline]
call_netdevice_notifiers net/core/dev.c:2019 [inline]
unregister_netdevice_many_notify+0xd48/0x17b4 net/core/dev.c:11043
unregister_netdevice_many net/core/dev.c:11099 [inline]
unregister_netdevice_queue+0x2d8/0x324 net/core/dev.c:10979
unregister_netdevice include/linux/netdevice.h:3158 [inline]
ser_release+0x1a4/0x238 drivers/net/caif/caif_serial.c:310
process_one_work+0x694/0x1204 kernel/workqueue.c:2627
process_scheduled_works kernel/workqueue.c:2700 [inline]
worker_thread+0x970/0xef4 kernel/workqueue.c:2781
kthread+0x288/0x310 kernel/kthread.c:388
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:857

The buggy address belongs to the object at ffff00011c808000
which belongs to the cache kmalloc-cg-2k of size 2048
The buggy address is located 32 bytes inside of
freed 2048-byte region [ffff00011c808000, ffff00011c808800)

The buggy address belongs to the physical page:
page:00000000a8975ac1 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x15c808
head:00000000a8975ac1 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff0000c23ef981
anon flags: 0x5ffc00000000840(slab|head|node=0|zone=2|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 05ffc00000000840 ffff0000c000f3c0 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000080008 00000001ffffffff ffff0000c23ef981
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff00011c807f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff00011c807f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff00011c808000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff00011c808080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff00011c808100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: e8f897f4afef Linux 6.8
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1729f41a180000
kernel config: https://syzkaller.appspot.com/x/.config?x=aba47157efb89052

dashboard link: https://syzkaller.appspot.com/bug?extid=2a81fdd5c6ddffee3894
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11f338d1180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/aa5aa46d901e/disk-e8f897f4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1c87fe0fa468/vmlinux-e8f897f4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/94beb1f39151/bzImage-e8f897f4.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2a81fd...@syzkaller.appspotmail.com

ieee802154 phy0 wpan0: encryption failed: -22
ieee802154 phy1 wpan1: encryption failed: -22
==================================================================

BUG: KASAN: slab-use-after-free in tty_write_room+0x35/0x90 drivers/tty/tty_ioctl.c:68
Read of size 8 at addr ffff88801f7e6020 by task aoe_tx0/1238

CPU: 1 PID: 1238 Comm: aoe_tx0 Not tainted 6.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x167/0x540 mm/kasan/report.c:488
kasan_report+0x142/0x180 mm/kasan/report.c:601
tty_write_room+0x35/0x90 drivers/tty/tty_ioctl.c:68
handle_tx+0x164/0x640 drivers/net/caif/caif_serial.c:226
__netdev_start_xmit include/linux/netdevice.h:4986 [inline]
netdev_start_xmit include/linux/netdevice.h:5000 [inline]
xmit_one net/core/dev.c:3547 [inline]
dev_hard_start_xmit+0x244/0x770 net/core/dev.c:3563
__dev_queue_xmit+0x19f4/0x3b10 net/core/dev.c:4351
dev_queue_xmit include/linux/netdevice.h:3169 [inline]
tx+0x6a/0x110 drivers/block/aoe/aoenet.c:62
kthread+0x23b/0x440 drivers/block/aoe/aoecmd.c:1229
kthread+0x2f1/0x390 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:243
</TASK>

Allocated by task 8605:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
__kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387
kasan_kmalloc include/linux/kasan.h:211 [inline]
kmalloc_trace+0x1d6/0x360 mm/slub.c:4012
kmalloc include/linux/slab.h:590 [inline]
kzalloc include/linux/slab.h:711 [inline]
alloc_tty_struct+0xa9/0x7d0 drivers/tty/tty_io.c:3116
tty_init_dev+0x5b/0x4c0 drivers/tty/tty_io.c:1415
ptmx_open+0xda/0x2c0 drivers/tty/pty.c:824
chrdev_open+0x5b2/0x630 fs/char_dev.c:414
do_dentry_open+0x909/0x15a0 fs/open.c:953
do_open fs/namei.c:3645 [inline]
path_openat+0x285f/0x3240 fs/namei.c:3802
do_filp_open+0x234/0x490 fs/namei.c:3829
do_sys_openat2+0x13e/0x1d0 fs/open.c:1404
do_sys_open fs/open.c:1419 [inline]
__do_sys_openat fs/open.c:1435 [inline]
__se_sys_openat fs/open.c:1430 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1430
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6f/0x77

Freed by task 5161:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:589
poison_slab_object+0xa6/0xe0 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2121 [inline]
slab_free mm/slub.c:4299 [inline]
kfree+0x14a/0x380 mm/slub.c:4409
process_one_work kernel/workqueue.c:2633 [inline]
process_scheduled_works+0x915/0x1420 kernel/workqueue.c:2706
worker_thread+0xa5f/0x1000 kernel/workqueue.c:2787
kthread+0x2f1/0x390 kernel/kthread.c:388
ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:243

Last potentially related work creation:

kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:551
insert_work+0x3e/0x330 kernel/workqueue.c:1653
__queue_work+0xbf4/0x1000 kernel/workqueue.c:1802
queue_work_on+0x14f/0x250 kernel/workqueue.c:1837
tty_release_struct+0xbc/0xe0 drivers/tty/tty_io.c:1707
tty_release+0xd0c/0x12c0 drivers/tty/tty_io.c:1867
__fput+0x42b/0x8a0 fs/file_table.c:376
__do_sys_close fs/open.c:1554 [inline]
__se_sys_close fs/open.c:1539 [inline]
__x64_sys_close+0x7e/0x110 fs/open.c:1539
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6f/0x77

The buggy address belongs to the object at ffff88801f7e6000

which belongs to the cache kmalloc-cg-2k of size 2048
The buggy address is located 32 bytes inside of

freed 2048-byte region [ffff88801f7e6000, ffff88801f7e6800)

The buggy address belongs to the physical page:

page:ffffea00007df800 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88801f7e5000 pfn:0x1f7e0
head:ffffea00007df800 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff8880217f6b81
flags: 0xfff00000000a40(workingset|slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000a40 ffff888014c4f3c0 ffffea0001ae3e10 ffffea0001ac3610
raw: ffff88801f7e5000 0000000000080006 00000001ffffffff ffff8880217f6b81

page dumped because: kasan: bad access detected

page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5098, tgid 5098 (syz-executor.4), ts 200401248275, free_ts 200027547453
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1533
prep_new_page mm/page_alloc.c:1540 [inline]
get_page_from_freelist+0x33ea/0x3580 mm/page_alloc.c:3311
__alloc_pages+0x255/0x680 mm/page_alloc.c:4569
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page+0x5f/0x160 mm/slub.c:2190
allocate_slab mm/slub.c:2354 [inline]
new_slab+0x84/0x2f0 mm/slub.c:2407
___slab_alloc+0xd17/0x13e0 mm/slub.c:3540
__slab_alloc mm/slub.c:3625 [inline]
__slab_alloc_node mm/slub.c:3678 [inline]
slab_alloc_node mm/slub.c:3850 [inline]
__do_kmalloc_node mm/slub.c:3980 [inline]
__kmalloc_node+0x2d6/0x4e0 mm/slub.c:3988
kmalloc_node include/linux/slab.h:610 [inline]
kvmalloc_node+0x72/0x190 mm/util.c:617
kvmalloc include/linux/slab.h:728 [inline]
kvmalloc_array include/linux/slab.h:746 [inline]
alloc_fdtable+0xe7/0x280 fs/file.c:136
dup_fd+0x839/0xc50 fs/file.c:354
copy_files+0x14f/0x2a0 kernel/fork.c:1789
copy_process+0x1c14/0x3fc0 kernel/fork.c:2485
kernel_clone+0x21d/0x8d0 kernel/fork.c:2902
__do_sys_clone kernel/fork.c:3045 [inline]
__se_sys_clone kernel/fork.c:3029 [inline]
__x64_sys_clone+0x258/0x2a0 kernel/fork.c:3029
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x6f/0x77
page last free pid 5111 tgid 5111 stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1140 [inline]
free_unref_page_prepare+0x968/0xa90 mm/page_alloc.c:2346
free_unref_page+0x37/0x3f0 mm/page_alloc.c:2486
__slab_free+0x349/0x410 mm/slub.c:4211
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x5e/0xc0 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:322
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3813 [inline]
slab_alloc_node mm/slub.c:3860 [inline]
kmem_cache_alloc_lru+0x172/0x350 mm/slub.c:3879
alloc_inode_sb include/linux/fs.h:3018 [inline]
alloc_inode fs/inode.c:262 [inline]
new_inode_pseudo+0x8b/0x1e0 fs/inode.c:1005
new_inode+0x22/0x1d0 fs/inode.c:1031
debugfs_get_inode fs/debugfs/inode.c:72 [inline]
__debugfs_create_file+0x14d/0x490 fs/debugfs/inode.c:437
add_sta_files net/mac80211/debugfs_netdev.c:850 [inline]
add_files net/mac80211/debugfs_netdev.c:959 [inline]
ieee80211_debugfs_add_netdev net/mac80211/debugfs_netdev.c:1012 [inline]
ieee80211_debugfs_recreate_netdev+0xc5a/0x1400 net/mac80211/debugfs_netdev.c:1045
ieee80211_if_add+0x988/0x1770 net/mac80211/iface.c:2169
ieee80211_register_hw+0x2fc7/0x3b80 net/mac80211/main.c:1418
mac80211_hwsim_new_radio+0x250e/0x4400 drivers/net/wireless/virtual/mac80211_hwsim.c:5329
hwsim_new_radio_nl+0xe4c/0x21d0 drivers/net/wireless/virtual/mac80211_hwsim.c:6010
genl_family_rcv_msg_doit net/netlink/genetlink.c:1113 [inline]
genl_family_rcv_msg net/netlink/genetlink.c:1193 [inline]
genl_rcv_msg+0xad8/0xe50 net/netlink/genetlink.c:1208

Memory state around the buggy address:

ffff88801f7e5f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88801f7e5f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88801f7e6000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88801f7e6080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88801f7e6100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

[Hillf Danton]

On Mon, 11 Mar 2024 07:34:21 -0700

> syzbot has found a reproducer for the following issue on:
>
> HEAD commit: e8f897f4afef Linux 6.8
> git tree: upstream

> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11f338d1180000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

--- x/drivers/net/caif/caif_serial.c
+++ y/drivers/net/caif/caif_serial.c
@@ -306,8 +306,11 @@ static void ser_release(struct work_stru
if (!list_empty(&list)) {
rtnl_lock();
list_for_each_entry_safe(ser, tmp, &list, node) {
+ struct tty_struct *tty = ser->tty;
+
dev_close(ser->dev);
unregister_netdevice(ser->dev);
+ tty_kref_put(tty);
debugfs_deinit(ser);
}
rtnl_unlock();
@@ -369,8 +372,6 @@ static void ldisc_close(struct tty_struc
{
struct ser_device *ser = tty->disc_data;

- tty_kref_put(ser->tty);
-
spin_lock(&ser_lock);
list_move(&ser->node, &ser_release_list);
spin_unlock(&ser_lock);
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+2a81fd...@syzkaller.appspotmail.com

Tested on:

commit: 855684c7 Merge tag 'x86_tdx_for_6.9' of git://git.kern..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=157056fa180000
kernel config: https://syzkaller.appspot.com/x/.config?x=2081781438cc5e28

dashboard link: https://syzkaller.appspot.com/bug?extid=2a81fdd5c6ddffee3894
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=12651646180000

Note: testing is done by a robot and is best-effort only.