syzbot

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BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:72 [inline]
BUG: KASAN: use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: use-after-free in refcount_read include/linux/refcount.h:147 [inline]
BUG: KASAN: use-after-free in skb_unref include/linux/skbuff.h:1203 [inline]
BUG: KASAN: use-after-free in kfree_skb_reason+0x3c/0x370 net/core/skbuff.c:887
Read of size 4 at addr ffff88801cec7c24 by task syz.1.977/8045

CPU: 0 PID: 8045 Comm: syz.1.977 Not tainted 6.1.140-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x220 mm/kasan/report.c:427
 kasan_report+0x10b/0x140 mm/kasan/report.c:531
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x27b/0x290 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
 refcount_read include/linux/refcount.h:147 [inline]
 skb_unref include/linux/skbuff.h:1203 [inline]
 kfree_skb_reason+0x3c/0x370 net/core/skbuff.c:887
 kfree_skb include/linux/skbuff.h:1220 [inline]
 nr_transmit_buffer+0x112/0x1a0 net/netrom/nr_out.c:210
 nr_establish_data_link+0x5e/0xb0 net/netrom/nr_out.c:227
 nr_connect+0x6e2/0xde0 net/netrom/af_netrom.c:723
 __sys_connect_file net/socket.c:2011 [inline]
 __sys_connect+0x389/0x410 net/socket.c:2028
 __do_sys_connect net/socket.c:2038 [inline]
 __se_sys_connect net/socket.c:2035 [inline]
 __x64_sys_connect+0x76/0x80 net/socket.c:2035
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fecc0b8e969
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fecc1a1c038 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007fecc0db6080 RCX: 00007fecc0b8e969
RDX: 0000000000000048 RSI: 0000200000000300 RDI: 0000000000000004
RBP: 00007fecc0c10ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fecc0db6080 R15: 00007ffdefd00e68
 </TASK>

Allocated by task 8045:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6b/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
 slab_alloc_node mm/slub.c:3398 [inline]
 kmem_cache_alloc_node+0x14d/0x320 mm/slub.c:3443
 __alloc_skb+0xfc/0x7e0 net/core/skbuff.c:505
 alloc_skb include/linux/skbuff.h:1271 [inline]
 nr_write_internal+0xca/0xcb0 net/netrom/nr_subr.c:144
 nr_establish_data_link+0x5e/0xb0 net/netrom/nr_out.c:227
 nr_connect+0x6e2/0xde0 net/netrom/af_netrom.c:723
 __sys_connect_file net/socket.c:2011 [inline]
 __sys_connect+0x389/0x410 net/socket.c:2028
 __do_sys_connect net/socket.c:2038 [inline]
 __se_sys_connect net/socket.c:2035 [inline]
 __x64_sys_connect+0x76/0x80 net/socket.c:2035
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 8045:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1724 [inline]
 slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1750
 slab_free mm/slub.c:3661 [inline]
 kmem_cache_free+0xf7/0x290 mm/slub.c:3683
 kfree_skb include/linux/skbuff.h:1220 [inline]
 nr_route_frame+0x45e/0x7d0 net/netrom/nr_route.c:820
 nr_transmit_buffer+0xe3/0x1a0 net/netrom/nr_out.c:209
 nr_establish_data_link+0x5e/0xb0 net/netrom/nr_out.c:227
 nr_connect+0x6e2/0xde0 net/netrom/af_netrom.c:723
 __sys_connect_file net/socket.c:2011 [inline]
 __sys_connect+0x389/0x410 net/socket.c:2028
 __do_sys_connect net/socket.c:2038 [inline]
 __se_sys_connect net/socket.c:2035 [inline]
 __x64_sys_connect+0x76/0x80 net/socket.c:2035
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88801cec7b40
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 228 bytes inside of
 240-byte region [ffff88801cec7b40, ffff88801cec7c30)

The buggy address belongs to the physical page:
page:ffffea000073b1c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88801cec7000 pfn:0x1cec7
memcg:ffff888023693281
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea0001f9ff08 ffffea0000b15ec8 ffff8880177c8500
raw: ffff88801cec7000 00000000000c0009 00000001ffffffff ffff888023693281
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 3631, tgid 3631 (udevd), ts 25105041728, free_ts 24963988546
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x1a26/0x1ac0 mm/page_alloc.c:4328
 __alloc_pages+0x1df/0x4e0 mm/page_alloc.c:5606
 alloc_slab_page+0x5d/0x160 mm/slub.c:1794
 allocate_slab mm/slub.c:1939 [inline]
 new_slab+0x87/0x2c0 mm/slub.c:1992
 ___slab_alloc+0xbc6/0x1220 mm/slub.c:3180
 __slab_alloc mm/slub.c:3279 [inline]
 slab_alloc_node mm/slub.c:3364 [inline]
 kmem_cache_alloc_node+0x1e5/0x320 mm/slub.c:3443
 __alloc_skb+0xfc/0x7e0 net/core/skbuff.c:505
 alloc_skb include/linux/skbuff.h:1271 [inline]
 alloc_skb_with_frags+0xa7/0x710 net/core/skbuff.c:6162
 sock_alloc_send_pskb+0x853/0x980 net/core/sock.c:2750
 unix_dgram_sendmsg+0x57e/0x18d0 net/unix/af_unix.c:1918
 sock_sendmsg_nosec net/socket.c:718 [inline]
 __sock_sendmsg net/socket.c:730 [inline]
 sock_write_iter+0x2b5/0x3a0 net/socket.c:1143
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x44c/0x960 fs/read_write.c:584
 ksys_write+0x143/0x240 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3384
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3479
 free_slab mm/slub.c:2031 [inline]
 discard_slab mm/slub.c:2037 [inline]
 __unfreeze_partials+0x1a5/0x200 mm/slub.c:2586
 put_cpu_partial+0x17c/0x250 mm/slub.c:2662
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x144/0x160 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1e/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x480 mm/slab.h:737
 slab_alloc_node mm/slub.c:3398 [inline]
 slab_alloc mm/slub.c:3406 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3413 [inline]
 kmem_cache_alloc+0x123/0x2f0 mm/slub.c:3422
 kmem_cache_zalloc include/linux/slab.h:689 [inline]
 __alloc_file+0x25/0x230 fs/file_table.c:138
 alloc_empty_file+0x90/0x180 fs/file_table.c:187
 path_openat+0xfc/0x2e70 fs/namei.c:3769
 do_filp_open+0x1c1/0x3c0 fs/namei.c:3810
 do_sys_openat2+0x142/0x490 fs/open.c:1318
 do_sys_open fs/open.c:1334 [inline]
 __do_sys_openat fs/open.c:1350 [inline]
 __se_sys_openat fs/open.c:1345 [inline]
 __x64_sys_openat+0x135/0x160 fs/open.c:1345
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81

Memory state around the buggy address:
 ffff88801cec7b00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff88801cec7b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88801cec7c00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
                               ^
 ffff88801cec7c80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801cec7d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
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