Re: [syzbot] [netfs?] KASAN: slab-use-after-free Read in netfs_unbuffered_write

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in netfs_clear_subrequests

==================================================================
BUG: KASAN: slab-use-after-free in __list_del_entry_valid_or_report+0x18a/0x1d0 lib/list_debug.c:49
Read of size 8 at addr ffff888023e99598 by task syz.0.17/6261

CPU: 0 UID: 0 PID: 6261 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
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/0x1d0 mm/kasan/report.c:595
 __list_del_entry_valid_or_report+0x18a/0x1d0 lib/list_debug.c:49
 __list_del_entry_valid include/linux/list.h:132 [inline]
 __list_del_entry include/linux/list.h:246 [inline]
 list_del include/linux/list.h:260 [inline]
 netfs_clear_subrequests+0x98/0x260 fs/netfs/objects.c:105
 netfs_unbuffered_write_done fs/netfs/direct_write.c:59 [inline]
 netfs_unbuffered_write+0x1358/0x21b0 fs/netfs/direct_write.c:203
 netfs_unbuffered_write_iter_locked+0x7e2/0xa90 fs/netfs/direct_write.c:295
 netfs_unbuffered_write_iter+0x442/0x740 fs/netfs/direct_write.c:387
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f85f8d9ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f85f9c79028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f85f9015fa0 RCX: 00007f85f8d9ce59
RDX: 00000000fffffdd8 RSI: 0000200000000540 RDI: 0000000000000003
RBP: 00007f85f8e32d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f85f9016038 R14: 00007f85f9015fa0 R15: 00007ffd265d5168
 </TASK>

Allocated by task 6261:
 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:4570 [inline]
 slab_alloc_node mm/slub.c:4899 [inline]
 kmem_cache_alloc_noprof+0x241/0x6e0 mm/slub.c:4906
 mempool_alloc_noprof+0x1b7/0x310 mm/mempool.c:566
 netfs_alloc_subrequest+0xc1/0x3c0 fs/netfs/objects.c:204
 netfs_prepare_write+0x76/0x780 fs/netfs/write_issue.c:172
 netfs_unbuffered_write+0x7b8/0x21b0 fs/netfs/direct_write.c:111
 netfs_unbuffered_write_iter_locked+0x7e2/0xa90 fs/netfs/direct_write.c:295
 netfs_unbuffered_write_iter+0x442/0x740 fs/netfs/direct_write.c:387
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6261:
 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:2689 [inline]
 slab_free mm/slub.c:6251 [inline]
 kmem_cache_free+0x127/0x6c0 mm/slub.c:6378
 mempool_free+0xde/0x130 mm/mempool.c:711
 netfs_free_subrequest fs/netfs/objects.c:239 [inline]
 netfs_put_subrequest+0x282/0x4c0 fs/netfs/objects.c:255
 netfs_unbuffered_write+0x1419/0x21b0 fs/netfs/direct_write.c:120
 netfs_unbuffered_write_iter_locked+0x7e2/0xa90 fs/netfs/direct_write.c:295
 netfs_unbuffered_write_iter+0x442/0x740 fs/netfs/direct_write.c:387
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888023e99540
 which belongs to the cache netfs_subrequest of size 200
The buggy address is located 88 bytes inside of
 freed 200-byte region [ffff888023e99540, ffff888023e99608)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888023e99680 pfn:0x23e98
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888023e980d9
flags: 0xfff00000000240(workingset|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000240 ffff888100ae5680 ffff888022d29408 ffff888022d29408
raw: ffff888023e99680 0000014000190012 00000000f5000000 ffff888023e980d9
head: 00fff00000000240 ffff888100ae5680 ffff888022d29408 ffff888022d29408
head: ffff888023e99680 0000014000190012 00000000f5000000 ffff888023e980d9
head: 00fff00000000001 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 6261, tgid 6260 (syz.0.17), ts 105932466205, free_ts 105884430549
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x11a6/0x3410 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5221
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7272
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4652
 alloc_from_pcs mm/slub.c:4750 [inline]
 slab_alloc_node mm/slub.c:4884 [inline]
 kmem_cache_alloc_noprof+0x480/0x6e0 mm/slub.c:4906
 mempool_alloc_noprof+0x1b7/0x310 mm/mempool.c:566
 netfs_alloc_subrequest+0xc1/0x3c0 fs/netfs/objects.c:204
 netfs_prepare_write+0x76/0x780 fs/netfs/write_issue.c:172
 netfs_unbuffered_write+0x7b8/0x21b0 fs/netfs/direct_write.c:111
 netfs_unbuffered_write_iter_locked+0x7e2/0xa90 fs/netfs/direct_write.c:295
 netfs_unbuffered_write_iter+0x442/0x740 fs/netfs/direct_write.c:387
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1070 fs/read_write.c:688
 ksys_write+0x12a/0x250 fs/read_write.c:740
page last free pid 40 tgid 40 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1397 [inline]
 __free_frozen_pages+0x794/0x10a0 mm/page_alloc.c:2938
 rcu_do_batch kernel/rcu/tree.c:2617 [inline]
 rcu_core+0x5a2/0x10d0 kernel/rcu/tree.c:2869
 handle_softirqs+0x1ea/0xa00 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:1061 [inline]
 sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1061
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697

Memory state around the buggy address:
 ffff888023e99480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888023e99500: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
>ffff888023e99580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff888023e99600: fb fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888023e99680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


Tested on:

commit:         f5e5d350 Merge tag 'spi-fix-v7.1-rc5' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1406497e580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8118209836970b54
dashboard link: https://syzkaller.appspot.com/bug?extid=3c74b1f0c372e98efc32
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14be29ec580000