KASAN: use-after-free Read in ext4_ext_insert

Date	Name	Commit	Repro	Result
2025/06/20	lts (merge base)	1c700860e8bc	C	[report] KASAN: use-after-free Read in ext4_ext_remove_space
2025/06/20	upstream (ToT)	75f5f23f8787	C	Didn't crash

Kernel	Title	Repro	Cause bisect	Count	Last	Reported	Patched	Status
linux-5.15	KASAN: use-after-free Read in ext4_ext_insert_extent			1	413d	413d	0/3	auto-obsoleted due to no activity on 2024/08/13 04:16
upstream	KASAN: use-after-free Read in ext4_ext_insert_extent ext4	C	done	5	11d	28d	0/29	upstream: reported C repro on 2025/05/25 18:12
android-5-10	KASAN: use-after-free Read in ext4_ext_insert_extent	syz		2	15d	100d	0/2	premoderation: reported syz repro on 2025/03/14 06:10
upstream	KASAN: slab-use-after-free Read in ext4_ext_insert_extent ext4			1	589d	585d	0/29	auto-obsoleted due to no activity on 2024/02/09 07:34

linux-5.15

KASAN: use-after-free Read in ext4_ext_insert_extent

413d

0/3

auto-obsoleted due to no activity on 2024/08/13 04:16

upstream

KASAN: use-after-free Read in ext4_ext_insert_extent ext4

done

11d

28d

0/29

upstream: reported C repro on 2025/05/25 18:12

android-5-10

KASAN: use-after-free Read in ext4_ext_insert_extent

syz

15d

100d

0/2

premoderation: reported syz repro on 2025/03/14 06:10

upstream

KASAN: slab-use-after-free Read in ext4_ext_insert_extent ext4

589d

585d

0/29

auto-obsoleted due to no activity on 2024/02/09 07:34

================================================================== BUG: KASAN: use-after-free in ext4_ext_insert_extent+0x204c/0x47a0 fs/ext4/extents.c:2157 Read of size 521328 at addr ffff8881333e1c3c by task syz.7.34/461 CPU: 0 PID: 461 Comm: syz.7.34 Not tainted 5.15.185-syzkaller-00339-ge678c93d43cc #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: <TASK> __dump_stack+0x21/0x30 lib/dump_stack.c:88 dump_stack_lvl+0xee/0x150 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+0xf1/0x140 mm/kasan/report.c:444 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x280/0x290 mm/kasan/generic.c:189 memmove+0x2d/0x70 mm/kasan/shadow.c:54 ext4_ext_insert_extent+0x204c/0x47a0 fs/ext4/extents.c:2157 ext4_ext_map_blocks+0x1574/0x6270 fs/ext4/extents.c:4360 ext4_map_blocks+0x97b/0x1b20 fs/ext4/inode.c:674 _ext4_get_block+0x1da/0x4e0 fs/ext4/inode.c:817 ext4_get_block+0x39/0x50 fs/ext4/inode.c:834 ext4_block_write_begin+0x556/0x1150 fs/ext4/inode.c:1102 ext4_write_begin+0x638/0x1220 fs/ext4/ext4_jbd2.h:-1 ext4_da_write_begin+0x2fa/0xb60 fs/ext4/inode.c:2988 generic_perform_write+0x2ad/0x670 mm/filemap.c:3857 ext4_buffered_write_iter+0x4ed/0x670 fs/ext4/file.c:270 ext4_file_write_iter+0x18c/0x14c0 fs/ext4/file.c:664 call_write_iter include/linux/fs.h:2204 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x802/0xf70 fs/read_write.c:594 ksys_write+0x140/0x240 fs/read_write.c:647 __do_sys_write fs/read_write.c:659 [inline] __se_sys_write fs/read_write.c:656 [inline] __x64_sys_write+0x7b/0x90 fs/read_write.c:656 x64_sys_call+0x8ef/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2 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: 0033:0x7fc689759929 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc6891a9038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fc689981080 RCX: 00007fc689759929 RDX: 00000000002a979d RSI: 0000200000000000 RDI: 0000000000000004 RBP: 00007fc6897dbb39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007fc689981080 R15: 00007fff144f7d88 </TASK> The buggy address belongs to the page: page:ffffea0004ccf840 refcount:2 mapcount:0 mapping:ffff8881093843d8 index:0x3f pfn:0x1333e1 memcg:ffff88811a340000 aops:def_blk_aops ino:700007 flags: 0x4000000000002014(uptodate|lru|private|zone=1) raw: 4000000000002014 ffffea0004c70d88 ffffea0004c70dc8 ffff8881093843d8 raw: 000000000000003f ffff888120413a80 00000002ffffffff ffff88811a340000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Movable, gfp_mask 0x108c48(GFP_NOFS|__GFP_NOFAIL|__GFP_HARDWALL|__GFP_MOVABLE), pid 461, ts 30352666406, free_ts 29959986356 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611 get_page_from_freelist+0x2cc5/0x2d50 mm/page_alloc.c:4485 __alloc_pages+0x18f/0x440 mm/page_alloc.c:5789 __alloc_pages_node include/linux/gfp.h:591 [inline] alloc_pages_node include/linux/gfp.h:605 [inline] alloc_pages include/linux/gfp.h:618 [inline] __page_cache_alloc include/linux/pagemap.h:305 [inline] pagecache_get_page+0x8c7/0xc20 mm/filemap.c:1946 find_or_create_page include/linux/pagemap.h:418 [inline] grow_dev_page fs/buffer.c:949 [inline] grow_buffers fs/buffer.c:1014 [inline] __getblk_slow fs/buffer.c:1041 [inline] __getblk_gfp+0x238/0x7d0 fs/buffer.c:1336 sb_getblk_gfp include/linux/buffer_head.h:368 [inline] ext4_ext_grow_indepth fs/ext4/extents.c:1330 [inline] ext4_ext_create_new_leaf fs/ext4/extents.c:1431 [inline] ext4_ext_insert_extent+0x110f/0x47a0 fs/ext4/extents.c:2102 ext4_ext_map_blocks+0x1574/0x6270 fs/ext4/extents.c:4360 ext4_map_blocks+0x97b/0x1b20 fs/ext4/inode.c:674 _ext4_get_block+0x1da/0x4e0 fs/ext4/inode.c:817 ext4_get_block+0x39/0x50 fs/ext4/inode.c:834 ext4_block_write_begin+0x556/0x1150 fs/ext4/inode.c:1102 ext4_write_begin+0x638/0x1220 fs/ext4/ext4_jbd2.h:-1 ext4_da_write_begin+0x2fa/0xb60 fs/ext4/inode.c:2988 generic_perform_write+0x2ad/0x670 mm/filemap.c:3857 ext4_buffered_write_iter+0x4ed/0x670 fs/ext4/file.c:270 page last free stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] free_pages_prepare mm/page_alloc.c:1472 [inline] free_pcp_prepare mm/page_alloc.c:1544 [inline] free_unref_page_prepare+0x542/0x550 mm/page_alloc.c:3534 free_unref_page_list+0x134/0x9d0 mm/page_alloc.c:3671 release_pages+0x1076/0x10d0 mm/swap.c:1009 free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:320 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline] tlb_flush_mmu_free mm/mmu_gather.c:240 [inline] tlb_flush_mmu mm/mmu_gather.c:247 [inline] tlb_finish_mmu+0x175/0x300 mm/mmu_gather.c:338 exit_mmap+0x40f/0x860 mm/mmap.c:3236 __mmput+0x93/0x320 kernel/fork.c:1180 mmput+0x50/0x150 kernel/fork.c:1203 exit_mm kernel/exit.c:554 [inline] do_exit+0x9ca/0x27a0 kernel/exit.c:867 do_group_exit+0x141/0x310 kernel/exit.c:1002 get_signal+0x66a/0x1480 kernel/signal.c:2907 arch_do_signal_or_restart+0xc1/0x10f0 arch/x86/kernel/signal.c:867 handle_signal_work kernel/entry/common.c:154 [inline] exit_to_user_mode_loop+0xa7/0xe0 kernel/entry/common.c:178 exit_to_user_mode_prepare+0x5a/0xa0 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: ffff888133405f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888133405f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff888133406000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ^ ffff888133406080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888133406100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ==================================================================

Crashes (1):
Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Assets (help?)	Manager	Title
2025/06/20 07:17	android13-5.15-lts	e678c93d43cc	ed3e87f7	.config	console log	report	syz / log			[disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)]	ci2-android-5-15	KASAN: use-after-free Read in ext4_ext_insert_extent

Crashes (1):

Assets (help?)