EXT4-fs (loop8): pa ffff88811c4aa738: logic 128, phys. 385, len 8
EXT4-fs error (device loop8): ext4_mb_release_inode_pa:4359: group 0, free 0, pa_free 1
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BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2596 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x3a6a/0x4920 fs/ext4/extents.c:2934
Read of size 4 at addr ffff8881350a6c18 by task syz.8.2233/8979

CPU: 0 PID: 8979 Comm: syz.8.2233 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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_rm_leaf fs/ext4/extents.c:2596 [inline]
 ext4_ext_remove_space+0x3a6a/0x4920 fs/ext4/extents.c:2934
 ext4_ext_truncate+0x169/0x1f0 fs/ext4/extents.c:4467
 ext4_truncate+0xaea/0x1290 fs/ext4/inode.c:4367
 ext4_truncate_failed_write fs/ext4/truncate.h:20 [inline]
 ext4_write_begin+0xd78/0x15a0 fs/ext4/inode.c:1276
 ext4_da_write_begin+0x455/0xe80 fs/ext4/inode.c:3033
 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:2066 [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: 0033:0x7f2b9f537fc9
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:00007f2b9dfa0038 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007f2b9f78efa0 RCX: 00007f2b9f537fc9
RDX: 00000000200000c1 RSI: 00002000000000c0 RDI: 0000000000000004
RBP: 00007f2b9f5baf91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000009000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2b9f78f038 R14: 00007f2b9f78efa0 R15: 00007ffce4986248

The buggy address belongs to the page:
page:ffffea0004d42980 refcount:1 mapcount:0 mapping:ffff888124b18930 index:0xf82 pfn:0x1350a6
aops:shmem_aops ino:c10 dentry name:"file0"
flags: 0x400000000008001e(referenced|uptodate|dirty|lru|swapbacked)
raw: 400000000008001e ffffea0004d42948 ffffea0004d429c8 ffff888124b18930
raw: 0000000000000f82 0000000000000000 00000001ffffffff ffff888127be2000
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff888127be2000
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x100cca(GFP_HIGHUSER_MOVABLE), pid 9004, ts 349444494543, free_ts 342000114783
 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:5370
 __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:1584
 shmem_alloc_and_acct_page+0x36f/0x7b0 mm/shmem.c:1609
 shmem_getpage_gfp+0x625/0x2110 mm/shmem.c:1922
 shmem_getpage mm/shmem.c:165 [inline]
 shmem_file_read_iter+0x27f/0x870 mm/shmem.c:2578
 call_read_iter include/linux/fs.h:2060 [inline]
 generic_file_splice_read+0x39f/0x590 fs/splice.c:311
 do_splice_to fs/splice.c:791 [inline]
 splice_direct_to_actor+0x3ff/0xb10 fs/splice.c:870
 do_splice_direct+0x1b3/0x2c0 fs/splice.c:979
 do_sendfile+0x8ca/0xf90 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0x18f/0x1f0 fs/read_write.c:1304
 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:969
 shmem_truncate_range mm/shmem.c:1073 [inline]
 shmem_evict_inode+0x1fd/0x9c0 mm/shmem.c:1173
 evict+0x478/0x910 fs/inode.c:612
 iput_final fs/inode.c:1736 [inline]
 iput+0x638/0x7c0 fs/inode.c:1762
 do_unlinkat+0x33f/0x670 fs/namei.c:4042
 __do_sys_unlink fs/namei.c:4082 [inline]
 __se_sys_unlink fs/namei.c:4080 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4080
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff8881350a6b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881350a6b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881350a6c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                            ^
 ffff8881350a6c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881350a6d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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