==================================================================
BUG: KASAN: slab-use-after-free in jffs2_prealloc_raw_node_refs+0x53b/0x800 fs/jffs2/malloc.c:205
Write of size 8 at addr ffff8880384f2350 by task jffs2_gcd_mtd0/6077

CPU: 0 UID: 0 PID: 6077 Comm: jffs2_gcd_mtd0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xba/0x230 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 jffs2_prealloc_raw_node_refs+0x53b/0x800 fs/jffs2/malloc.c:205
 jffs2_mark_erased_block fs/jffs2/erase.c:428 [inline]
 jffs2_erase_pending_blocks+0x13cb/0x24c0 fs/jffs2/erase.c:116
 jffs2_garbage_collect_pass+0x6dd/0x2150 fs/jffs2/gc.c:253
 jffs2_garbage_collect_thread+0x67c/0x710 fs/jffs2/background.c:155
 kthread+0x388/0x470 kernel/kthread.c:467
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6076:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5238 [inline]
 __kmalloc_noprof+0x3e7/0x7b0 mm/slub.c:5250
 kmalloc_noprof include/linux/slab.h:954 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 jffs2_do_mount_fs+0x117/0x2280 fs/jffs2/build.c:387
 jffs2_do_fill_super+0x573/0xbd0 fs/jffs2/fs.c:574
 mtd_get_sb+0x18f/0x410 drivers/mtd/mtdsuper.c:57
 get_tree_mtd+0x5e9/0x830 drivers/mtd/mtdsuper.c:141
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3763 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3839
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4338
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5987:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2692 [inline]
 slab_free mm/slub.c:6143 [inline]
 kfree+0x1c1/0x6c0 mm/slub.c:6461
 jffs2_put_super+0x9a/0x170 fs/jffs2/super.c:337
 generic_shutdown_super+0x13d/0x2d0 fs/super.c:646
 kill_mtd_super+0x23/0x70 drivers/mtd/mtdsuper.c:174
 jffs2_kill_sb+0x96/0xb0 fs/jffs2/super.c:350
 deactivate_locked_super+0xbc/0x130 fs/super.c:476
 cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
 exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880384f2000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 848 bytes inside of
 freed 4096-byte region [ffff8880384f2000, ffff8880384f3000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x384f0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88813fe1d140 dead000000000122 0000000000000000
raw: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88813fe1d140 dead000000000122 0000000000000000
head: 0000000000000000 0000000800040004 00000000f5000000 0000000000000000
head: 0080000000000003 ffffea0000e13c01 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000008
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 6076, tgid 6075 (syz-executor.0), ts 103978821782, free_ts 65583217454
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889
 prep_new_page mm/page_alloc.c:1897 [inline]
 get_page_from_freelist+0x28bb/0x2950 mm/page_alloc.c:3962
 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250
 alloc_slab_page mm/slub.c:3269 [inline]
 allocate_slab+0x77/0x660 mm/slub.c:3458
 new_slab mm/slub.c:3516 [inline]
 refill_objects+0x334/0x3c0 mm/slub.c:7153
 refill_sheaf mm/slub.c:2818 [inline]
 __pcs_replace_empty_main+0x328/0x5f0 mm/slub.c:4592
 alloc_from_pcs mm/slub.c:4695 [inline]
 slab_alloc_node mm/slub.c:4829 [inline]
 __kmalloc_cache_noprof+0x44e/0x690 mm/slub.c:5353
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 jffs2_init_fs_context+0x4f/0xc0 fs/jffs2/super.c:314
 alloc_fs_context+0x9d5/0xd50 fs/fs_context.c:295
 do_new_mount+0x187/0xd30 fs/namespace.c:3819
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4338
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5726 tgid 5726 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xfe3/0x1170 mm/page_alloc.c:2978
 __slab_free+0x24f/0x2a0 mm/slub.c:5551
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4515 [inline]
 slab_alloc_node mm/slub.c:4844 [inline]
 kmem_cache_alloc_noprof+0x33b/0x680 mm/slub.c:4851
 vm_area_alloc+0x24/0x140 mm/vma_init.c:32
 __mmap_new_vma mm/vma.c:2517 [inline]
 __mmap_region mm/vma.c:2759 [inline]
 mmap_region+0x112c/0x2230 mm/vma.c:2837
 do_mmap+0xc2f/0x10c0 mm/mmap.c:559
 vm_mmap_pgoff+0x2cc/0x4f0 mm/util.c:581
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff8880384f2200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880384f2280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880384f2300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff8880384f2380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880384f2400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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