================================================================== BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:837 [inline] BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:953 Read of size 4 at addr ffff88814698a8e8 by task syz.1.2129/8855 CPU: 1 PID: 8855 Comm: syz.1.2129 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 Call Trace: __dump_stack+0x21/0x24 lib/dump_stack.c:88 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106 print_address_description+0x71/0x1e0 mm/kasan/report.c:316 print_report+0x4a/0x60 mm/kasan/report.c:418 kasan_report+0x122/0x150 mm/kasan/report.c:522 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350 ext4_ext_binsearch fs/ext4/extents.c:837 [inline] ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:953 ext4_ext_map_blocks+0x1dc/0x6060 fs/ext4/extents.c:4166 ext4_map_blocks+0x398/0x1b60 fs/ext4/inode.c:606 _ext4_get_block+0x1da/0x4e0 fs/ext4/inode.c:822 ext4_get_block+0x39/0x50 fs/ext4/inode.c:839 ext4_block_write_begin+0x56e/0x1270 fs/ext4/inode.c:1124 ext4_write_begin+0x5ee/0xf70 fs/ext4/ext4_jbd2.h:-1 ext4_da_write_begin+0x3e1/0x8b0 fs/ext4/inode.c:3001 generic_perform_write+0x2f6/0x6d0 mm/filemap.c:3882 ext4_buffered_write_iter+0x36f/0x660 fs/ext4/file.c:285 ext4_file_write_iter+0x18f/0x13d0 fs/ext4/file.c:-1 do_iter_readv_writev fs/read_write.c:-1 [inline] do_iter_write+0x650/0xb10 fs/read_write.c:861 vfs_writev+0x30b/0x590 fs/read_write.c:934 do_writev+0x14a/0x2b0 fs/read_write.c:977 __do_sys_writev fs/read_write.c:1050 [inline] __se_sys_writev fs/read_write.c:1047 [inline] __x64_sys_writev+0x7d/0x90 fs/read_write.c:1047 x64_sys_call+0xad/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:21 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7f5aa8b8eba9 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:00007f5aa9aee038 EFLAGS: 00000246 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: 00007f5aa8dd5fa0 RCX: 00007f5aa8b8eba9 RDX: 0000000000000004 RSI: 0000200000000500 RDI: 0000000000000004 RBP: 00007f5aa8c11e19 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f5aa8dd6038 R14: 00007f5aa8dd5fa0 R15: 00007fff72c51ec8 The buggy address belongs to the physical page: page:ffffea00051a6280 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x1 pfn:0x14698a flags: 0x4000000000000000(zone=1) raw: 4000000000000000 ffffea0004d66488 ffffea0004cb9008 0000000000000000 raw: 0000000000000001 0000000000000000 00000000ffffff7f 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as freed page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 8877, tgid 8851 (syz.1.2129), ts 582720307503, free_ts 582901241795 set_page_owner include/linux/page_owner.h:33 [inline] post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2643 prep_new_page+0x1c/0x110 mm/page_alloc.c:2650 get_page_from_freelist+0x2c7b/0x2cf0 mm/page_alloc.c:4554 __alloc_pages+0x1c3/0x450 mm/page_alloc.c:5868 __folio_alloc+0x12/0x40 mm/page_alloc.c:5900 __folio_alloc_node include/linux/gfp.h:245 [inline] folio_alloc include/linux/gfp.h:274 [inline] shmem_alloc_folio mm/shmem.c:1601 [inline] shmem_alloc_and_acct_folio+0x650/0x870 mm/shmem.c:1626 shmem_get_folio_gfp+0x119f/0x2230 mm/shmem.c:1955 shmem_get_folio mm/shmem.c:2086 [inline] shmem_write_begin+0xea/0x2c0 mm/shmem.c:2571 generic_perform_write+0x2f6/0x6d0 mm/filemap.c:3882 __generic_file_write_iter+0x227/0x580 mm/filemap.c:4011 generic_file_write_iter+0xae/0x310 mm/filemap.c:4043 call_write_iter include/linux/fs.h:2282 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x5db/0xca0 fs/read_write.c:584 ksys_write+0x140/0x240 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] __se_sys_write fs/read_write.c:646 [inline] __x64_sys_write+0x7b/0x90 fs/read_write.c:646 x64_sys_call+0x27b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2 do_syscall_x64 arch/x86/entry/common.c:51 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81 page last free stack trace: reset_page_owner include/linux/page_owner.h:26 [inline] free_pages_prepare mm/page_alloc.c:1551 [inline] free_pcp_prepare mm/page_alloc.c:1625 [inline] free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3589 free_unref_page_list+0x112/0x8b0 mm/page_alloc.c:3740 release_pages+0xad1/0xb20 mm/swap.c:1043 __pagevec_release+0x71/0xe0 mm/swap.c:1063 pagevec_release include/linux/pagevec.h:71 [inline] folio_batch_release include/linux/pagevec.h:135 [inline] shmem_undo_range+0x51a/0x1470 mm/shmem.c:955 shmem_truncate_range mm/shmem.c:1071 [inline] shmem_evict_inode+0x242/0xa10 mm/shmem.c:1180 evict+0x493/0x890 fs/inode.c:705 iput_final fs/inode.c:1834 [inline] iput+0x620/0x670 fs/inode.c:1860 dentry_unlink_inode+0x33d/0x3f0 fs/dcache.c:405 __dentry_kill+0x460/0x670 fs/dcache.c:611 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1 dput+0x42/0x80 fs/dcache.c:918 __fput+0x5be/0x8f0 fs/file_table.c:328 ____fput+0x15/0x20 fs/file_table.c:348 task_work_run+0x1db/0x240 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177 Memory state around the buggy address: ffff88814698a780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88814698a800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff88814698a880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff88814698a900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88814698a980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== EXT4-fs error (device loop1): ext4_map_blocks:635: inode #18: block 1: comm syz.1.2129: lblock 1 mapped to illegal pblock 1 (length 1)