================================================================== BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:827 [inline] BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:946 Read of size 4 at addr ffff88814dc66018 by task syz.2.7329/21983 CPU: 1 PID: 21983 Comm: syz.2.7329 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: __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+0xf1/0x140 mm/kasan/report.c:444 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308 ext4_ext_binsearch fs/ext4/extents.c:827 [inline] ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:946 ext4_ext_map_blocks+0x207/0x61e0 fs/ext4/extents.c:4172 ext4_map_blocks+0x3b4/0x1b30 fs/ext4/inode.c:601 _ext4_get_block+0x1ea/0x540 fs/ext4/inode.c:817 ext4_get_block_unwritten+0x2a/0x40 fs/ext4/inode.c:848 ext4_block_write_begin+0x563/0x1160 fs/ext4/inode.c:1102 ext4_write_begin+0x65a/0x12e0 fs/ext4/ext4_jbd2.h:-1 ext4_da_write_begin+0x321/0xbf0 fs/ext4/inode.c:2988 generic_perform_write+0x2b7/0x690 mm/filemap.c:3870 ext4_buffered_write_iter+0x4ed/0x670 fs/ext4/file.c:270 ext4_file_write_iter+0x440/0x1540 fs/ext4/file.c:-1 do_iter_readv_writev+0x478/0x5f0 fs/read_write.c:-1 do_iter_write+0x1fa/0x7b0 fs/read_write.c:855 vfs_writev+0x2df/0x570 fs/read_write.c:928 do_pwritev fs/read_write.c:1025 [inline] __do_sys_pwritev2 fs/read_write.c:1084 [inline] __se_sys_pwritev2+0x1af/0x2b0 fs/read_write.c:1075 __x64_sys_pwritev2+0xbf/0xd0 fs/read_write.c:1075 x64_sys_call+0x346/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:329 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: 0033:0x7f8f1f41a799 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:00007f8f1de54028 EFLAGS: 00000246 ORIG_RAX: 0000000000000148 RAX: ffffffffffffffda RBX: 00007f8f1f694090 RCX: 00007f8f1f41a799 RDX: 0000000000000001 RSI: 0000200000000100 RDI: 0000000000000006 RBP: 00007f8f1f4b0c99 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000005405 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f8f1f694128 R14: 00007f8f1f694090 R15: 00007ffe20540f28 The buggy address belongs to the page: page:ffffea0005371980 refcount:1 mapcount:0 mapping:ffff88812472c9a8 index:0x1d6e pfn:0x14dc66 memcg:ffff88811bab33c0 aops:shmem_aops ino:e4e dentry name:"memfd:syzkaller" flags: 0x400000000008001e(referenced|uptodate|dirty|lru|swapbacked|zone=1) raw: 400000000008001e ffffea0005371948 ffffea00053719c8 ffff88812472c9a8 raw: 0000000000001d6e 0000000000000000 00000001ffffffff ffff88811bab33c0 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Movable, gfp_mask 0x100cca(GFP_HIGHUSER_MOVABLE), pid 21980, ts 897205818834, free_ts 895579260992 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+0x2d3a/0x2dc0 mm/page_alloc.c:4485 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5822 __alloc_pages_node include/linux/gfp.h:595 [inline] alloc_pages_node include/linux/gfp.h:609 [inline] alloc_pages include/linux/gfp.h:622 [inline] shmem_alloc_page mm/shmem.c:1591 [inline] shmem_alloc_and_acct_page+0x4a2/0x8d0 mm/shmem.c:1616 shmem_getpage_gfp+0xfe5/0x2310 mm/shmem.c:1912 shmem_getpage mm/shmem.c:156 [inline] shmem_write_begin+0xce/0x1b0 mm/shmem.c:2480 generic_perform_write+0x2b7/0x690 mm/filemap.c:3870 __generic_file_write_iter+0x268/0x480 mm/filemap.c:3998 generic_file_write_iter+0xa9/0x1d0 mm/filemap.c:4030 call_write_iter include/linux/fs.h:2212 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x835/0xfd0 fs/read_write.c:594 ksys_write+0x149/0x250 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 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+0x13a/0x9d0 mm/page_alloc.c:3671 release_pages+0x1006/0x1060 mm/swap.c:1015 __pagevec_release+0x71/0xe0 mm/swap.c:1035 pagevec_release include/linux/pagevec.h:81 [inline] shmem_undo_range+0x595/0x1470 mm/shmem.c:969 shmem_truncate_range mm/shmem.c:1068 [inline] shmem_evict_inode+0x21a/0xa10 mm/shmem.c:1150 evict+0x4c9/0x8d0 fs/inode.c:650 iput_final fs/inode.c:1779 [inline] iput+0x635/0x7c0 fs/inode.c:1805 dentry_unlink_inode+0x32f/0x3e0 fs/dcache.c:380 __dentry_kill+0x44f/0x650 fs/dcache.c:586 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1 dput+0x47/0x90 fs/dcache.c:893 __fput+0x580/0x8b0 fs/file_table.c:319 ____fput+0x15/0x20 fs/file_table.c:339 task_work_run+0x127/0x190 kernel/task_work.c:188 exit_task_work include/linux/task_work.h:33 [inline] do_exit+0xa9e/0x27e0 kernel/exit.c:889 Memory state around the buggy address: ffff88814dc65f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88814dc65f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff88814dc66000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ^ ffff88814dc66080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88814dc66100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ================================================================== EXT4-fs error (device loop2): ext4_ext_split:1074: inode #15: comm syz.2.7329: p_ext > EXT_MAX_EXTENT! EXT4-fs error (device loop2): mb_free_blocks:1874: group 0, inode 15: block 337:freeing already freed block (bit 21); block bitmap corrupt. EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 203 with max blocks 1 with error 117 EXT4-fs (loop2): This should not happen!! Data will be lost