KASAN: use-after-free Read in ring_buffer_read

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KASAN: use-after-free Write in ring_buffer_read_page actionable prio:normal trace	22				1	96d	88d	0/29	upstream: reported on 2026/06/02 13:45
RAX: ffffffffffffffda RBX: 00007f52c7c44fa0 RCX: 00007f52c79bd159
RDX: 0000000000000002 RSI: 0000200000001340 RDI: 0000000000000004
RBP: 00007f52c7a54024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f52c7c45038 R14: 00007f52c7c44fa0 R15: 00007fff241f8208
 </TASK>
---[ end trace 55fe909543438e88 ]---
==================================================================
BUG: KASAN: use-after-free in rb_event_ts_length kernel/trace/ring_buffer.c:221 [inline]
BUG: KASAN: use-after-free in ring_buffer_read_page+0x115d/0x1210 kernel/trace/ring_buffer.c:5689
Read of size 4 at addr ffff88812472b155 by task syz.4.2569/6486

CPU: 1 PID: 6486 Comm: syz.4.2569 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x10f/0x150 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 rb_event_ts_length kernel/trace/ring_buffer.c:221 [inline]
 ring_buffer_read_page+0x115d/0x1210 kernel/trace/ring_buffer.c:5689
 tracing_buffers_read+0x2fb/0x810 kernel/trace/trace.c:8148
 do_loop_readv_writev fs/read_write.c:-1 [inline]
 do_iter_read+0x50b/0x780 fs/read_write.c:792
 vfs_readv fs/read_write.c:910 [inline]
 do_readv+0x25d/0x450 fs/read_write.c:947
 __do_sys_readv fs/read_write.c:1038 [inline]
 __se_sys_readv fs/read_write.c:1035 [inline]
 __x64_sys_readv+0x7d/0x90 fs/read_write.c:1035
 x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:20
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f52c79bd159
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:00007f52c6416028 EFLAGS: 00000246 ORIG_RAX: 0000000000000013
RAX: ffffffffffffffda RBX: 00007f52c7c44fa0 RCX: 00007f52c79bd159
RDX: 0000000000000002 RSI: 0000200000001340 RDI: 0000000000000004
RBP: 00007f52c7a54024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f52c7c45038 R14: 00007f52c7c44fa0 R15: 00007fff241f8208
 </TASK>

Allocated by task 6198:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 __kasan_slab_alloc+0xb7/0xe0 mm/kasan/common.c:466
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
 mempool_alloc_slab+0x1d/0x30 mm/mempool.c:513
 mempool_alloc+0x167/0x4c0 mm/mempool.c:393
 bio_alloc_bioset+0x124/0x910 block/bio.c:469
 bio_alloc include/linux/bio.h:429 [inline]
 z_erofs_submit_queue fs/erofs/zdata.c:1456 [inline]
 z_erofs_runqueue+0xd44/0x11f0 fs/erofs/zdata.c:1505
 z_erofs_readpage+0x25d/0x4d0 fs/erofs/zdata.c:1604
 filemap_read_page+0xd3/0x330 mm/filemap.c:2401
 filemap_fault+0x1316/0x1cc0 mm/filemap.c:3263
 __do_fault+0x25f/0x2f0 mm/memory.c:4195
 do_read_fault mm/memory.c:4568 [inline]
 do_fault mm/memory.c:4709 [inline]
 handle_pte_fault+0x1bc0/0x2770 mm/memory.c:4923
 __handle_mm_fault mm/memory.c:-1 [inline]
 do_handle_mm_fault+0x1b3b/0x1e30 mm/memory.c:5345
 handle_mm_fault include/linux/mm.h:1847 [inline]
 faultin_page mm/gup.c:976 [inline]
 __get_user_pages+0x80e/0x10c0 mm/gup.c:1197
 populate_vma_page_range mm/gup.c:1529 [inline]
 __mm_populate+0x324/0x470 mm/gup.c:1638
 do_mlock+0x4a6/0x580 mm/mlock.c:689
 __do_sys_mlock mm/mlock.c:697 [inline]
 __se_sys_mlock mm/mlock.c:695 [inline]
 __x64_sys_mlock+0x60/0x70 mm/mlock.c:695
 x64_sys_call+0x27b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:150
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Freed by task 6198:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kmem_cache_free+0x100/0x320 mm/slub.c:3544
 mempool_free_slab+0x1d/0x30 mm/mempool.c:520
 mempool_free+0xd5/0x330 mm/mempool.c:502
 bio_free+0x255/0x360 block/bio.c:239
 bio_put+0x91/0x610 block/bio.c:700
 z_erofs_decompressqueue_endio+0x568/0x5b0 fs/erofs/zdata.c:970
 bio_endio+0x732/0x810 block/bio.c:1478
 submit_bio_checks+0x25c/0x11e0 block/blk-core.c:910
 __submit_bio+0x59f/0x900 block/blk-core.c:922
 __submit_bio_noacct_mq block/blk-core.c:1008 [inline]
 submit_bio_noacct+0x6b7/0x800 block/blk-core.c:1038
 submit_bio+0x367/0x620 block/blk-core.c:1110
 z_erofs_submit_queue fs/erofs/zdata.c:1484 [inline]
 z_erofs_runqueue+0x10e2/0x11f0 fs/erofs/zdata.c:1505
 z_erofs_readpage+0x25d/0x4d0 fs/erofs/zdata.c:1604
 filemap_read_page+0xd3/0x330 mm/filemap.c:2401
 filemap_fault+0x1316/0x1cc0 mm/filemap.c:3263
 __do_fault+0x25f/0x2f0 mm/memory.c:4195
 do_read_fault mm/memory.c:4568 [inline]
 do_fault mm/memory.c:4709 [inline]
 handle_pte_fault+0x1bc0/0x2770 mm/memory.c:4923
 __handle_mm_fault mm/memory.c:-1 [inline]
 do_handle_mm_fault+0x1b3b/0x1e30 mm/memory.c:5345
 handle_mm_fault include/linux/mm.h:1847 [inline]
 faultin_page mm/gup.c:976 [inline]
 __get_user_pages+0x80e/0x10c0 mm/gup.c:1197
 populate_vma_page_range mm/gup.c:1529 [inline]
 __mm_populate+0x324/0x470 mm/gup.c:1638
 do_mlock+0x4a6/0x580 mm/mlock.c:689
 __do_sys_mlock mm/mlock.c:697 [inline]
 __se_sys_mlock mm/mlock.c:695 [inline]
 __x64_sys_mlock+0x60/0x70 mm/mlock.c:695
 x64_sys_call+0x27b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:150
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff88812472b140
 which belongs to the cache bio-224 of size 224
The buggy address is located 21 bytes inside of
 224-byte region [ffff88812472b140, ffff88812472b220)
The buggy address belongs to the page:
page:ffffea000491cac0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12472b
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000122 ffff8881081abc80
raw: 0000000000000000 00000000000c000c 00000001ffffffff 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 0x192800(GFP_NOWAIT|__GFP_NOWARN|__GFP_NORETRY|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 6198, ts 169425525745, free_ts 168920277642
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa0/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x3ac/0x840 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0x138/0x260 mm/slub.c:3260
 mempool_alloc_slab+0x1d/0x30 mm/mempool.c:513
 mempool_alloc+0x167/0x4c0 mm/mempool.c:393
 bio_alloc_bioset+0x124/0x910 block/bio.c:469
 bio_alloc include/linux/bio.h:429 [inline]
 z_erofs_submit_queue fs/erofs/zdata.c:1456 [inline]
 z_erofs_runqueue+0xd44/0x11f0 fs/erofs/zdata.c:1505
 z_erofs_readpage+0x25d/0x4d0 fs/erofs/zdata.c:1604
 filemap_read_page+0xd3/0x330 mm/filemap.c:2401
 filemap_fault+0x1316/0x1cc0 mm/filemap.c:3263
 __do_fault+0x25f/0x2f0 mm/memory.c:4195
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1474 [inline]
 free_pcp_prepare mm/page_alloc.c:1546 [inline]
 free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536
 free_unref_page+0xae/0x540 mm/page_alloc.c:3618
 free_the_page mm/page_alloc.c:805 [inline]
 __free_pages+0x6c/0x100 mm/page_alloc.c:5900
 __vunmap+0x801/0x980 mm/vmalloc.c:2660
 __vfree mm/vmalloc.c:2709 [inline]
 vfree+0x8b/0xc0 mm/vmalloc.c:2740
 kvfree+0x26/0x40 mm/util.c:659
 memslot_rmap_free arch/x86/kvm/x86.c:11795 [inline]
 kvm_arch_free_memslot+0x3f/0x150 arch/x86/kvm/x86.c:11804
 kvm_free_memslot virt/kvm/kvm_main.c:934 [inline]
 kvm_free_memslots virt/kvm/kvm_main.c:948 [inline]
 kvm_destroy_vm virt/kvm/kvm_main.c:1254 [inline]
 kvm_put_kvm+0xc58/0x1190 virt/kvm/kvm_main.c:1283
 kvm_vm_release+0x46/0x50 virt/kvm/kvm_main.c:1306
 __fput+0x22b/0x900 fs/file_table.c:311
 ____fput+0x15/0x20 fs/file_table.c:339
 task_work_run+0x127/0x190 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0xd0/0xe0 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0x87/0xd0 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86

Memory state around the buggy address:
 ffff88812472b000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812472b080: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff88812472b100: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
                                                 ^
 ffff88812472b180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88812472b200: fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================