==================================================================
BUG: KASAN: slab-use-after-free in netfs_unbuffered_write+0x1bde/0x21b0 fs/netfs/direct_write.c:119
Read of size 2 at addr ffff8880550ae1e4 by task syz.1.4467/20528

CPU: 1 UID: 0 PID: 20528 Comm: syz.1.4467 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 netfs_unbuffered_write+0x1bde/0x21b0 fs/netfs/direct_write.c:119
 netfs_unbuffered_write_iter_locked+0x7cd/0xa80 fs/netfs/direct_write.c:294
 netfs_unbuffered_write_iter+0x442/0x720 fs/netfs/direct_write.c:386
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
 iter_file_splice_write+0x830/0x10b0 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x192/0x690 fs/splice.c:1159
 splice_direct_to_actor+0x345/0xa30 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x174/0x240 fs/splice.c:1228
 vfs_copy_file_range+0xc1b/0x1840 fs/read_write.c:1633
 __do_sys_copy_file_range+0x1a1/0x460 fs/read_write.c:1682
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7f54fec
Code: Unable to access opcode bytes at 0xf7f54fc2.
RSP: 002b:00000000f53f550c EFLAGS: 00000292 ORIG_RAX: 0000000000000179
RAX: ffffffffffffffda RBX: 0000000000000007 RCX: 0000000000000000
RDX: 0000000000000005 RSI: 0000000000000000 RDI: 00000000e003e45c
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000292 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 20528:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4612 [inline]
 slab_alloc_node mm/slub.c:4945 [inline]
 kmem_cache_alloc_noprof+0x26b/0x6a0 mm/slub.c:4959
 mempool_alloc_noprof+0x1b7/0x310 mm/mempool.c:559
 netfs_alloc_subrequest+0xc1/0x3c0 fs/netfs/objects.c:204
 netfs_prepare_write+0x76/0x780 fs/netfs/write_issue.c:172
 netfs_unbuffered_write+0x7ba/0x21b0 fs/netfs/direct_write.c:111
 netfs_unbuffered_write_iter_locked+0x7cd/0xa80 fs/netfs/direct_write.c:294
 netfs_unbuffered_write_iter+0x442/0x720 fs/netfs/direct_write.c:386
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
 iter_file_splice_write+0x830/0x10b0 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x192/0x690 fs/splice.c:1159
 splice_direct_to_actor+0x345/0xa30 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x174/0x240 fs/splice.c:1228
 vfs_copy_file_range+0xc1b/0x1840 fs/read_write.c:1633
 __do_sys_copy_file_range+0x1a1/0x460 fs/read_write.c:1682
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Freed by task 20528:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2705 [inline]
 slab_free mm/slub.c:6405 [inline]
 kmem_cache_free+0x127/0x6b0 mm/slub.c:6532
 mempool_free+0xde/0x130 mm/mempool.c:704
 netfs_free_subrequest fs/netfs/objects.c:239 [inline]
 netfs_put_subrequest+0x282/0x4b0 fs/netfs/objects.c:255
 netfs_unbuffered_write+0x13c0/0x21b0 fs/netfs/direct_write.c:118
 netfs_unbuffered_write_iter_locked+0x7cd/0xa80 fs/netfs/direct_write.c:294
 netfs_unbuffered_write_iter+0x442/0x720 fs/netfs/direct_write.c:386
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
 iter_file_splice_write+0x830/0x10b0 fs/splice.c:736
 do_splice_from fs/splice.c:936 [inline]
 direct_splice_actor+0x192/0x690 fs/splice.c:1159
 splice_direct_to_actor+0x345/0xa30 fs/splice.c:1103
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x174/0x240 fs/splice.c:1228
 vfs_copy_file_range+0xc1b/0x1840 fs/read_write.c:1633
 __do_sys_copy_file_range+0x1a1/0x460 fs/read_write.c:1682
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

The buggy address belongs to the object at ffff8880550ae140
 which belongs to the cache netfs_subrequest of size 200
The buggy address is located 164 bytes inside of
 freed 200-byte region [ffff8880550ae140, ffff8880550ae208)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff8880550ae640 pfn:0x550ae
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff8880550ae0d9
flags: 0x4fff00000000240(workingset|head|node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000240 ffff8880416dadc0 ffffea0001414810 ffffea0001af7290
raw: ffff8880550ae640 000001400019000a 00000000f5000000 ffff8880550ae0d9
head: 04fff00000000240 ffff8880416dadc0 ffffea0001414810 ffffea0001af7290
head: ffff8880550ae640 000001400019000a 00000000f5000000 ffff8880550ae0d9
head: 04fff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd2880(GFP_NOWAIT|__GFP_FS|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 10081, tgid 10060 (syz.5.1231), ts 278756343771, free_ts 277351386639
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1859
 prep_new_page mm/page_alloc.c:1867 [inline]
 get_page_from_freelist+0xf48/0x3530 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x299/0x2dc0 mm/page_alloc.c:5304
 alloc_slab_page mm/slub.c:3294 [inline]
 allocate_slab mm/slub.c:3408 [inline]
 new_slab+0xa2/0x650 mm/slub.c:3454
 refill_objects+0xe3/0x410 mm/slub.c:7338
 refill_sheaf mm/slub.c:2832 [inline]
 __pcs_replace_empty_main+0x376/0x680 mm/slub.c:4703
 alloc_from_pcs mm/slub.c:4801 [inline]
 slab_alloc_node mm/slub.c:4933 [inline]
 kmem_cache_alloc_noprof+0x46e/0x6a0 mm/slub.c:4959
 mempool_alloc_noprof+0x1b7/0x310 mm/mempool.c:559
 netfs_alloc_subrequest+0xc1/0x3c0 fs/netfs/objects.c:204
 netfs_dispatch_unbuffered_reads fs/netfs/direct_read.c:58 [inline]
 netfs_unbuffered_read fs/netfs/direct_read.c:128 [inline]
 netfs_unbuffered_read_iter_locked+0x5cc/0x11d0 fs/netfs/direct_read.c:211
 netfs_unbuffered_read_iter+0xc5/0x100 fs/netfs/direct_read.c:250
 v9fs_file_read_iter+0xbf/0x100 fs/9p/vfs_file.c:366
 copy_splice_read+0x4ba/0xbb0 fs/splice.c:362
 v9fs_file_splice_read+0xc8/0xe0 fs/9p/vfs_file.c:390
 do_splice_read fs/splice.c:980 [inline]
 do_splice_read+0x285/0x370 fs/splice.c:954
 splice_direct_to_actor+0x2a1/0xa30 fs/splice.c:1084
page last free pid 0 tgid 0 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0x79f/0x1090 mm/page_alloc.c:2950
 rcu_do_batch kernel/rcu/tree.c:2645 [inline]
 rcu_core+0x5a2/0x10d0 kernel/rcu/tree.c:2897
 handle_softirqs+0x1ea/0x9b0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x162/0x210 kernel/softirq.c:735
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1062
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674

Memory state around the buggy address:
 ffff8880550ae080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880550ae100: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff8880550ae180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff8880550ae200: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880550ae280: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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