Message-ID: <CANypQFaiPBCsB67pzF4pTspjLPAue9droyqp4JtvGoXaVNmr8A@mail.gmail.com>
Date: Wed, 16 Jul 2025 18:09:28 +0800
From: Jiaming Zhang <r772577952@...il.com>
To: chao@...nel.org, jaegeuk@...nel.org, 
	linux-f2fs-devel@...ts.sourceforge.net
Cc: linux-kernel@...r.kernel.org, syzkaller@...glegroups.com
Subject: [Linux Kernel Bug] KASAN: slab-out-of-bounds Read in f2fs_get_dnode_of_data

Dear Linux kernel developers and maintainers:

We are writing to report a slab-out-of-bounds bug discovered in the f2fs
subsystem with a modified syzkaller.

This bug was initially found in Linux kernel v5.15 (commit
8bb7eca972ad531c9b149c0a51ab43a417385813), and it is reproducible on the
latest version (v6.16-rc6, commit 347e9f5043c89695b01e66b3ed111755afcf1911).

The log, kernel config, syzkaller reproducer, and C reproducer are attached
to this email to help analysis. The KASAN report from v6.16-rc6, formatted
by syz-symbolize, is listed below.

==================================================================
BUG: KASAN: slab-out-of-bounds in data_blkaddr fs/f2fs/f2fs.h:3053 [inline]
BUG: KASAN: slab-out-of-bounds in f2fs_data_blkaddr fs/f2fs/f2fs.h:3058
[inline]
BUG: KASAN: slab-out-of-bounds in f2fs_get_dnode_of_data+0x1a09/0x1c40
fs/f2fs/node.c:855
Read of size 4 at addr ffff8880464770b0 by task repro/9734

CPU: 1 UID: 0 PID: 9734 Comm: repro Not tainted 6.16.0-rc6 #1 PREEMPT(full)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1
04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x1c1/0x2a0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x17e/0x800 mm/kasan/report.c:480
 kasan_report+0x147/0x180 mm/kasan/report.c:593
 data_blkaddr fs/f2fs/f2fs.h:3053 [inline]
 f2fs_data_blkaddr fs/f2fs/f2fs.h:3058 [inline]
 f2fs_get_dnode_of_data+0x1a09/0x1c40 fs/f2fs/node.c:855
 f2fs_reserve_block+0x53/0x310 fs/f2fs/data.c:1195
 prepare_write_begin fs/f2fs/data.c:3395 [inline]
 f2fs_write_begin+0xf39/0x2190 fs/f2fs/data.c:3594
 generic_perform_write+0x2c7/0x910 mm/filemap.c:4112
 f2fs_buffered_write_iter fs/f2fs/file.c:4988 [inline]
 f2fs_file_write_iter+0x1ec8/0x2410 fs/f2fs/file.c:5216
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x546/0xa90 fs/read_write.c:686
 ksys_write+0x149/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf3/0x3d0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x459a0d
Code: c3 e8 b7 23 00 00 0f 1f 80 00 00 00 00 f3 0f 1e fa 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffeb41adbd8 EFLAGS: 00000287 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ffeb41ade38 RCX: 0000000000459a0d
RDX: 00000000fffffd6e RSI: 0000000020000180 RDI: 0000000000000005
RBP: 00007ffeb41adbf0 R08: 00007ffeb41adbf0 R09: 00007ffeb41adbf0
R10: 0000000000000000 R11: 0000000000000287 R12: 0000000000000001
R13: 00007ffeb41ade28 R14: 00000000004de790 R15: 0000000000000001
 </TASK>

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:319 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:345
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4148 [inline]
 slab_alloc_node mm/slub.c:4197 [inline]
 kmem_cache_alloc_noprof+0x1c1/0x3c0 mm/slub.c:4204
 __kernfs_new_node+0xd7/0x7e0 fs/kernfs/dir.c:637
 kernfs_new_node+0x102/0x210 fs/kernfs/dir.c:713
 kernfs_create_dir_ns+0x44/0x130 fs/kernfs/dir.c:1083
 sysfs_create_dir_ns+0x123/0x280 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:73 [inline]
 kobject_add_internal+0x40c/0x940 lib/kobject.c:240
 kobject_add_varg lib/kobject.c:374 [inline]
 kobject_init_and_add+0x125/0x190 lib/kobject.c:457
 netdev_queue_add_kobject net/core/net-sysfs.c:1976 [inline]
 netdev_queue_update_kobjects+0x249/0x6c0 net/core/net-sysfs.c:2035
 register_queue_kobjects net/core/net-sysfs.c:2098 [inline]
 netdev_register_kobject+0x236/0x2f0 net/core/net-sysfs.c:2340
 register_netdevice+0x126c/0x1ae0 net/core/dev.c:11105
 register_netdev+0x40/0x60 net/core/dev.c:11221
 ip6gre_init_net+0x271/0x3a0 net/ipv6/ip6_gre.c:1629
 ops_init+0x359/0x5c0 net/core/net_namespace.c:138
 __register_pernet_operations net/core/net_namespace.c:1284 [inline]
 register_pernet_operations+0x336/0x800 net/core/net_namespace.c:1361
 register_pernet_device+0x2a/0x80 net/core/net_namespace.c:1448
 ip6gre_init+0x22/0x120 net/ipv6/ip6_gre.c:2355
 do_one_initcall+0x233/0x860 init/main.c:1274
 do_initcall_level+0x137/0x1f0 init/main.c:1336
 do_initcalls+0x69/0xd0 init/main.c:1352
 kernel_init_freeable+0x3d9/0x570 init/main.c:1584
 kernel_init+0x1d/0x2a0 init/main.c:1474
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff888046477000
 which belongs to the cache kernfs_node_cache of size 176
The buggy address is located 0 bytes to the right of
 allocated 176-byte region [ffff888046477000, ffff8880464770b0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x46477
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000000 ffff8880404188c0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000110011 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask
0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1
(swapper/0), ts 7313974045, free_ts 6400501225
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1704
 prep_new_page mm/page_alloc.c:1712 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3669
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4959
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2419
 alloc_slab_page mm/slub.c:2451 [inline]
 allocate_slab+0x8a/0x3b0 mm/slub.c:2619
 new_slab mm/slub.c:2673 [inline]
 ___slab_alloc+0xbfc/0x1480 mm/slub.c:3859
 __slab_alloc mm/slub.c:3949 [inline]
 __slab_alloc_node mm/slub.c:4024 [inline]
 slab_alloc_node mm/slub.c:4185 [inline]
 kmem_cache_alloc_noprof+0x283/0x3c0 mm/slub.c:4204
 __kernfs_new_node+0xd7/0x7e0 fs/kernfs/dir.c:637
 kernfs_new_node+0x102/0x210 fs/kernfs/dir.c:713
 kernfs_create_dir_ns+0x44/0x130 fs/kernfs/dir.c:1083
 sysfs_create_dir_ns+0x123/0x280 fs/sysfs/dir.c:59
 create_dir lib/kobject.c:73 [inline]
 kobject_add_internal+0x40c/0x940 lib/kobject.c:240
 kobject_add_varg lib/kobject.c:374 [inline]
 kobject_init_and_add+0x125/0x190 lib/kobject.c:457
 netdev_queue_add_kobject net/core/net-sysfs.c:1976 [inline]
 netdev_queue_update_kobjects+0x249/0x6c0 net/core/net-sysfs.c:2035
 register_queue_kobjects net/core/net-sysfs.c:2098 [inline]
 netdev_register_kobject+0x236/0x2f0 net/core/net-sysfs.c:2340
 register_netdevice+0x126c/0x1ae0 net/core/dev.c:11105
page last free pid 1235 tgid 1235 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1248 [inline]
 __free_frozen_pages+0xc8e/0xe90 mm/page_alloc.c:2706
 kasan_depopulate_vmalloc_pte+0x74/0xa0 mm/kasan/shadow.c:472
 apply_to_pte_range mm/memory.c:3032 [inline]
 apply_to_pmd_range mm/memory.c:3076 [inline]
 apply_to_pud_range mm/memory.c:3112 [inline]
 apply_to_p4d_range mm/memory.c:3148 [inline]
 __apply_to_page_range+0xb8a/0x1360 mm/memory.c:3184
 kasan_release_vmalloc+0xa5/0xd0 mm/kasan/shadow.c:593
 kasan_release_vmalloc_node mm/vmalloc.c:2249 [inline]
 purge_vmap_node+0x20f/0x8f0 mm/vmalloc.c:2266
 __purge_vmap_area_lazy+0x7a4/0xb40 mm/vmalloc.c:2356
 drain_vmap_area_work+0x27/0x40 mm/vmalloc.c:2390
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff888046476f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888046477000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888046477080: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc 00 00
                                     ^
 ffff888046477100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888046477180: 00 00 00 00 fc fc fc fc fc fc fc fc 00 00 00 00
==================================================================

Please let me know if any further information is required.

Best Regards,
Jiaming Zhang.

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