EXT4-fs error (device loop6): ext4_map_blocks:629: inode #2: block 16: comm syz.6.1110: lblock 0 mapped to illegal pblock 16 (length 1)
EXT4-fs error (device loop6): ext4_map_blocks:629: inode #2: block 16: comm syz.6.1110: lblock 0 mapped to illegal pblock 16 (length 1)
==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945
Read of size 4 at addr ffff88812e0b5dcc by task syz.6.1110/5013

CPU: 0 PID: 5013 Comm: syz.6.1110 Tainted: G        W         5.10.236-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
 ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945
 ext4_ext_map_blocks+0x1de/0x5d40 fs/ext4/extents.c:4159
 ext4_map_blocks+0x993/0x1b80 fs/ext4/inode.c:673
 _ext4_get_block+0x1bb/0x4b0 fs/ext4/inode.c:816
 ext4_get_block_unwritten+0x2a/0x40 fs/ext4/inode.c:847
 ext4_block_write_begin+0x567/0x1330 fs/ext4/inode.c:1100
 ext4_write_begin+0x651/0x1550 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x455/0xe80 fs/ext4/inode.c:3032
 generic_perform_write+0x2be/0x510 mm/filemap.c:3509
 ext4_buffered_write_iter+0x4b8/0x640 fs/ext4/file.c:271
 ext4_file_write_iter+0x536/0x1980 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2058 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x725/0xd60 fs/read_write.c:605
 ksys_pwrite64 fs/read_write.c:712 [inline]
 __do_sys_pwrite64 fs/read_write.c:722 [inline]
 __se_sys_pwrite64 fs/read_write.c:719 [inline]
 __x64_sys_pwrite64+0x191/0x220 fs/read_write.c:719
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f9e84cc3969
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:00007f9e8332c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007f9e84eeafa0 RCX: 00007f9e84cc3969
RDX: 0000000000000001 RSI: 0000200000000140 RDI: 0000000000000009
RBP: 00007f9e84d45ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000200980 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9e84eeafa0 R15: 00007ffc2d126eb8

The buggy address belongs to the page:
page:ffffea0004b82d40 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12e0b5
flags: 0x4000000000000000()
raw: 4000000000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000001 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 5011, ts 176748007631, free_ts 176800010187
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5349
 __alloc_pages include/linux/gfp.h:544 [inline]
 __alloc_pages_node include/linux/gfp.h:557 [inline]
 alloc_pages_node include/linux/gfp.h:571 [inline]
 alloc_pages include/linux/gfp.h:590 [inline]
 shmem_alloc_page+0x1b1/0x300 mm/shmem.c:1580
 shmem_alloc_and_acct_page+0x36f/0x7b0 mm/shmem.c:1605
 shmem_getpage_gfp+0x625/0x2110 mm/shmem.c:1918
 shmem_getpage mm/shmem.c:161 [inline]
 shmem_write_begin+0xce/0x1b0 mm/shmem.c:2497
 generic_perform_write+0x2be/0x510 mm/filemap.c:3509
 __generic_file_write_iter+0x24b/0x480 mm/filemap.c:3638
 generic_file_write_iter+0xa9/0x1d0 mm/filemap.c:3670
 call_write_iter include/linux/fs.h:2058 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x725/0xd60 fs/read_write.c:605
 ksys_write+0x140/0x240 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 free_pcp_prepare mm/page_alloc.c:1421 [inline]
 free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336
 free_unref_page_list+0x12e/0x9b0 mm/page_alloc.c:3443
 release_pages+0xe38/0xe80 mm/swap.c:1103
 __pagevec_release+0x71/0xe0 mm/swap.c:1123
 pagevec_release include/linux/pagevec.h:88 [inline]
 shmem_undo_range+0x6e1/0x1760 mm/shmem.c:965
 shmem_truncate_range mm/shmem.c:1069 [inline]
 shmem_evict_inode+0x1fd/0x9c0 mm/shmem.c:1169
 evict+0x478/0x910 fs/inode.c:612
 iput_final fs/inode.c:1736 [inline]
 iput+0x638/0x7c0 fs/inode.c:1762
 dentry_unlink_inode+0x2cf/0x380 fs/dcache.c:378
 __dentry_kill+0x44f/0x650 fs/dcache.c:583
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x42/0x80 fs/dcache.c:883
 __fput+0x4fe/0x770 fs/file_table.c:294
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172

Memory state around the buggy address:
 ffff88812e0b5c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812e0b5d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812e0b5d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88812e0b5e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812e0b5e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop6): ext4_map_blocks:739: inode #15: block 2050: comm syz.6.1110: lblock 2050 mapped to illegal pblock 2050 (length 1)
EXT4-fs error (device loop6): ext4_map_blocks:739: inode #15: block 1: comm syz.6.1110: lblock 1 mapped to illegal pblock 1 (length 1)