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BUG: KASAN: use-after-free in gsm_cleanup_mux+0x5c7/0x5f0 drivers/tty/n_gsm.c:2259
Read of size 4 at addr ffff88800f27400c by task syz-executor.0/1633

CPU: 1 PID: 1633 Comm: syz-executor.0 Not tainted 5.19.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x44/0x60 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:313 [inline]
 print_report.cold+0x2c0/0x74d mm/kasan/report.c:429
 kasan_report+0xdd/0x190 mm/kasan/report.c:491
 gsm_cleanup_mux+0x5c7/0x5f0 drivers/tty/n_gsm.c:2259
 gsm_config drivers/tty/n_gsm.c:2512 [inline]
 gsmld_ioctl+0x3ce/0x1030 drivers/tty/n_gsm.c:2827
 tty_ioctl+0x5bc/0x1140 drivers/tty/tty_io.c:2787
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x125/0x190 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7fe65367c859
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fe6531de0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fe65379c050 RCX: 00007fe65367c859
RDX: 0000000020000040 RSI: 00000000404c4701 RDI: 0000000000000005
RBP: 00007fe6536d8ad0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007fe65379c050 R15: 00007ffc6b12c758
 </TASK>

Allocated by task 1625:
 kasan_save_stack+0x33/0x50 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:436 [inline]
 ____kasan_kmalloc mm/kasan/common.c:515 [inline]
 __kasan_kmalloc+0xab/0xd0 mm/kasan/common.c:524
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:733 [inline]
 gsm_dlci_alloc+0x41/0x3d0 drivers/tty/n_gsm.c:1832
 gsm_activate_mux drivers/tty/n_gsm.c:2313 [inline]
 gsm_config drivers/tty/n_gsm.c:2536 [inline]
 gsmld_ioctl+0xad0/0x1030 drivers/tty/n_gsm.c:2827
 tty_ioctl+0x5bc/0x1140 drivers/tty/tty_io.c:2787
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x125/0x190 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Freed by task 1625:
 kasan_save_stack+0x33/0x50 mm/kasan/common.c:38
 kasan_set_track+0x25/0x30 mm/kasan/common.c:45
 kasan_set_free_info+0x24/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free mm/kasan/common.c:366 [inline]
 ____kasan_slab_free+0x125/0x1a0 mm/kasan/common.c:328
 kasan_slab_free include/linux/kasan.h:200 [inline]
 slab_free_hook mm/slub.c:1727 [inline]
 slab_free_freelist_hook+0xae/0x1e0 mm/slub.c:1753
 slab_free mm/slub.c:3507 [inline]
 kfree+0xcb/0x590 mm/slub.c:4555
 dlci_put drivers/tty/n_gsm.c:1888 [inline]
 gsm_dlci_release drivers/tty/n_gsm.c:1921 [inline]
 gsm_cleanup_mux+0x27d/0x5f0 drivers/tty/n_gsm.c:2276
 gsm_config drivers/tty/n_gsm.c:2512 [inline]
 gsmld_ioctl+0x3ce/0x1030 drivers/tty/n_gsm.c:2827
 tty_ioctl+0x5bc/0x1140 drivers/tty/tty_io.c:2787
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __x64_sys_ioctl+0x125/0x190 fs/ioctl.c:856
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

The buggy address belongs to the object at ffff88800f274000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 12 bytes inside of
 2048-byte region [ffff88800f274000, ffff88800f274800)

The buggy address belongs to the physical page:
page:ffffea00003c9c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xf270
head:ffffea00003c9c00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea0000319000 dead000000000002 ffff888008842000
raw: 0000000000000000 0000000080080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 938, tgid 938 (udevd), ts 6695580468, free_ts 6693891901
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x203/0x2f0 mm/page_alloc.c:2449
 prep_new_page mm/page_alloc.c:2456 [inline]
 get_page_from_freelist+0x16fb/0x3410 mm/page_alloc.c:4198
 __alloc_pages+0x1d0/0x4c0 mm/page_alloc.c:5426
 alloc_slab_page mm/slub.c:1797 [inline]
 allocate_slab+0x26c/0x390 mm/slub.c:1942
 new_slab mm/slub.c:2002 [inline]
 ___slab_alloc+0x955/0xce0 mm/slub.c:3002
 __slab_alloc.constprop.0+0x45/0x80 mm/slub.c:3089
 slab_alloc_node mm/slub.c:3180 [inline]
 __kmalloc_node_track_caller+0x349/0x490 mm/slub.c:4950
 kmalloc_reserve net/core/skbuff.c:354 [inline]
 __alloc_skb+0x8c/0x270 net/core/skbuff.c:426
 alloc_skb include/linux/skbuff.h:1426 [inline]
 netlink_alloc_large_skb net/netlink/af_netlink.c:1191 [inline]
 netlink_sendmsg+0x848/0xc60 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg+0xb2/0xe0 net/socket.c:734
 ____sys_sendmsg+0x604/0x810 net/socket.c:2492
 ___sys_sendmsg+0xf4/0x170 net/socket.c:2546
 __sys_sendmsg+0xdb/0x170 net/socket.c:2575
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1371 [inline]
 free_pcp_prepare+0x4be/0xc70 mm/page_alloc.c:1421
 free_unref_page_prepare mm/page_alloc.c:3343 [inline]
 free_unref_page+0x1d/0x530 mm/page_alloc.c:3438
 __unfreeze_partials+0x193/0x1b0 mm/slub.c:2521
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x6a/0x170 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x17a/0x1a0 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0xa6/0xc0 mm/kasan/common.c:446
 kasan_slab_alloc include/linux/kasan.h:224 [inline]
 slab_post_alloc_hook mm/slab.h:750 [inline]
 slab_alloc_node mm/slub.c:3214 [inline]
 slab_alloc mm/slub.c:3222 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3229 [inline]
 kmem_cache_alloc+0x244/0x3b0 mm/slub.c:3239
 getname_flags.part.0+0x4a/0x430 fs/namei.c:139
 do_sys_openat2+0xec/0x410 fs/open.c:1272
 do_sys_open fs/open.c:1294 [inline]
 __do_sys_openat fs/open.c:1310 [inline]
 __se_sys_openat fs/open.c:1305 [inline]
 __x64_sys_openat+0x134/0x1d0 fs/open.c:1305
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0x80 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Memory state around the buggy address:
 ffff88800f273f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88800f273f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88800f274000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff88800f274080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88800f274100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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