================================================================== 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 ffff88813e2c1ba4 by task syz.5.5255/17372 CPU: 1 PID: 17372 Comm: syz.5.5255 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 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:4166 ext4_map_blocks+0x988/0x1b30 fs/ext4/inode.c:674 mpage_map_one_extent fs/ext4/inode.c:2421 [inline] mpage_map_and_submit_extent fs/ext4/inode.c:2474 [inline] ext4_writepages+0x123f/0x3090 fs/ext4/inode.c:2842 do_writepages+0x473/0x6c0 mm/page-writeback.c:2388 filemap_fdatawrite_wbc+0x1f4/0x250 mm/filemap.c:409 __filemap_fdatawrite_range mm/filemap.c:442 [inline] filemap_write_and_wait_range+0x126/0x3d0 mm/filemap.c:713 ext4_punch_hole+0x120/0xbd0 fs/ext4/inode.c:4032 ext4_fallocate+0x2b6/0x1de0 fs/ext4/extents.c:4765 vfs_fallocate+0x4b4/0x590 fs/open.c:309 madvise_remove mm/madvise.c:964 [inline] madvise_vma_behavior mm/madvise.c:988 [inline] madvise_walk_vmas mm/madvise.c:1218 [inline] do_madvise+0x1435/0x2420 mm/madvise.c:1396 __do_sys_madvise mm/madvise.c:1409 [inline] __se_sys_madvise mm/madvise.c:1407 [inline] __x64_sys_madvise+0xa9/0xc0 mm/madvise.c:1407 x64_sys_call+0x89b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:29 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: 0033:0x7f1046b95cb9 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:00007f10455f2028 EFLAGS: 00000246 ORIG_RAX: 000000000000001c RAX: ffffffffffffffda RBX: 00007f1046e10fa0 RCX: 00007f1046b95cb9 RDX: 0000000000000009 RSI: 0000000000600003 RDI: 0000200000000000 RBP: 00007f1046c03bf7 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f1046e11038 R14: 00007f1046e10fa0 R15: 00007fffd43b4b28 The buggy address belongs to the page: page:ffffea0004f8b040 refcount:0 mapcount:0 mapping:0000000000000000 index:0x100 pfn:0x13e2c1 flags: 0x4000000000000000(zone=1) raw: 4000000000000000 dead000000000100 dead000000000122 0000000000000000 raw: 0000000000000100 0000000000000000 00000000ffffffff 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 0x100cca(GFP_HIGHUSER_MOVABLE), pid 16968, ts 542971682708, free_ts 549555280386 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:5808 __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 __kernel_write+0x510/0x950 fs/read_write.c:539 __dump_emit+0x246/0x370 fs/coredump.c:880 dump_emit+0x383/0x3f0 fs/coredump.c:917 dump_user_range+0x86/0x1c0 fs/coredump.c:954 elf_core_dump+0x2a8f/0x2fd0 fs/binfmt_elf.c:2285 do_coredump+0x1452/0x2950 fs/coredump.c:831 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:1014 __pagevec_release+0x71/0xe0 mm/swap.c:1034 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: ffff88813e2c1a80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88813e2c1b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff88813e2c1b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff88813e2c1c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff88813e2c1c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ==================================================================