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KASAN: out-of-bounds Read in ext4_ext_remove_space

Status: upstream: reported C repro on 2023/08/04 22:38
Bug presence: origin:upstream
Labels: missing-backport
[Documentation on labels]
Reported-by: syzbot+b08e3d059329c5bfbfdb@syzkaller.appspotmail.com
First crash: 707d, last: 4d16h
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (4)
Date Name Commit Repro Result
2024/04/13 android13-5.15-lts (ToT) 993bed180178 C [report] KASAN: out-of-bounds Read in ext4_ext_remove_space
2023/09/01 lts (merge base) f6f7927ac664 C [report] KASAN: out-of-bounds Read in ext4_ext_remove_space
2023/09/01 upstream (ToT) 99d99825fc07 C [report] KASAN: out-of-bounds Read in ext4_ext_remove_space
2024/04/13 upstream (ToT) 7efd0a74039f C Didn't crash
▶ ▼ Similar bugs (6)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: out-of-bounds Read in ext4_ext_remove_space C error 7 2d20h 660d 0/2 upstream: reported C repro on 2023/09/02 13:17
upstream KASAN: out-of-bounds Read in ext4_ext_remove_space ext4 C error done 8 536d 710d 25/29 fixed on 2024/02/16 19:40
android-6-1 KASAN: out-of-bounds Read in ext4_ext_remove_space missing-backport C error error 6 247d 679d 0/2 auto-obsoleted due to no activity on 2025/01/27 17:01
linux-5.15 KASAN: out-of-bounds Read in ext4_ext_remove_space missing-backport origin:upstream C done 5 35d 519d 0/3 upstream: reported C repro on 2024/01/21 16:07
linux-6.1 KASAN: out-of-bounds Read in ext4_ext_remove_space origin:upstream missing-backport C done 7 13d 537d 0/3 upstream: reported C repro on 2024/01/03 15:27
upstream KASAN: slab-use-after-free Read in ext4_ext_remove_space ext4 11 8d13h 84d 0/29 upstream: reported on 2025/03/31 11:15
▶ ▼ Last patch testing requests (7)
Created Duration User Patch Repo Result
2025/05/24 18:13 6m retest repro android13-5.15-lts report log
2025/05/24 18:13 19m retest repro android13-5.15-lts report log
2025/04/09 13:50 1h03m retest repro android13-5.15-lts report log
2025/04/09 13:50 7m retest repro android13-5.15-lts report log
2025/03/13 05:59 6m retest repro android13-5.15-lts report log
2025/03/13 05:59 5m retest repro android13-5.15-lts report log
2025/02/02 13:37 21m retest repro android13-5.15-lts OK log
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2024/05/30 20:00 6m bisect fix android13-5.15-lts error job log
2023/10/20 03:00 35m bisect fix android13-5.15-lts OK (0) job log log

Sample crash report:
EXT4-fs error (device loop0): ext4_free_blocks:6225: comm syz-executor327: Freeing blocks not in datazone - block = 41, count = 1
EXT4-fs (loop0): Remounting filesystem read-only
==================================================================
BUG: KASAN: out-of-bounds in ext4_ext_rm_leaf fs/ext4/extents.c:2711 [inline]
BUG: KASAN: out-of-bounds in ext4_ext_remove_space+0x2149/0x4a60 fs/ext4/extents.c:2933
Read of size 18446744073709551604 at addr ffff888123763018 by task syz-executor327/312

CPU: 0 PID: 312 Comm: syz-executor327 Not tainted 5.15.166-syzkaller-01786-g6ddd8fde5711 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1c0 lib/dump_stack.c:106
 print_address_description+0x87/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x179/0x1c0 mm/kasan/report.c:444
 kasan_check_range+0x293/0x2a0 mm/kasan/generic.c:189
 memmove+0x2d/0x70 mm/kasan/shadow.c:54
 ext4_ext_rm_leaf fs/ext4/extents.c:2711 [inline]
 ext4_ext_remove_space+0x2149/0x4a60 fs/ext4/extents.c:2933
 ext4_punch_hole+0x794/0xbf0 fs/ext4/inode.c:4130
 ext4_fallocate+0x30c/0x1f10 fs/ext4/extents.c:4742
 vfs_fallocate+0x492/0x570 fs/open.c:309
 ksys_fallocate fs/open.c:332 [inline]
 __do_sys_fallocate fs/open.c:340 [inline]
 __se_sys_fallocate fs/open.c:338 [inline]
 __x64_sys_fallocate+0xc0/0x110 fs/open.c:338
 x64_sys_call+0x783/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:286
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f33719fd539
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 1f 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f337198d218 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f3371a7f6f8 RCX: 00007f33719fd539
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000004
RBP: 00007f3371a7f6f0 R08: 00007ffc83280107 R09: 0000000000000000
R10: 0000000000001a00 R11: 0000000000000246 R12: 00007f3371a4abb4
R13: 0000000000000010 R14: 0031656c69662f2e R15: 6f6f6c2f7665642f
 </TASK>

The buggy address belongs to the page:
page:ffffea00048dd8c0 refcount:2 mapcount:0 mapping:ffff88810928fa18 index:0x27 pfn:0x123763
memcg:ffff888100210000
aops:def_blk_aops ino:700000
flags: 0x4000000000002036(referenced|uptodate|lru|active|private|zone=1)
raw: 4000000000002036 ffffea00048dd848 ffffea00042fcb88 ffff88810928fa18
raw: 0000000000000027 ffff8881091cbb28 00000002ffffffff ffff888100210000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x108c48(GFP_NOFS|__GFP_NOFAIL|__GFP_HARDWALL|__GFP_MOVABLE), pid 307, ts 26676093861, free_ts 19910763086
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4485
 __alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5779
 __alloc_pages_node include/linux/gfp.h:591 [inline]
 alloc_pages_node include/linux/gfp.h:605 [inline]
 alloc_pages include/linux/gfp.h:618 [inline]
 __page_cache_alloc include/linux/pagemap.h:305 [inline]
 pagecache_get_page+0xb18/0xeb0 mm/filemap.c:1946
 find_or_create_page include/linux/pagemap.h:418 [inline]
 grow_dev_page fs/buffer.c:949 [inline]
 grow_buffers fs/buffer.c:1014 [inline]
 __getblk_slow fs/buffer.c:1041 [inline]
 __getblk_gfp+0x21e/0x7c0 fs/buffer.c:1336
 sb_getblk_gfp include/linux/buffer_head.h:368 [inline]
 ext4_ext_grow_indepth fs/ext4/extents.c:1328 [inline]
 ext4_ext_create_new_leaf fs/ext4/extents.c:1429 [inline]
 ext4_ext_insert_extent+0xf7a/0x4b10 fs/ext4/extents.c:2099
 ext4_split_extent_at+0x80e/0x10f0 fs/ext4/extents.c:3230
 ext4_split_extent+0x1bd/0x4e0 fs/ext4/extents.c:3331
 ext4_split_convert_extents fs/ext4/extents.c:3692 [inline]
 ext4_ext_handle_unwritten_extents fs/ext4/extents.c:3854 [inline]
 ext4_ext_map_blocks+0x223e/0x7450 fs/ext4/extents.c:4209
 ext4_map_blocks+0xa60/0x1c70 fs/ext4/inode.c:673
 _ext4_get_block+0x23b/0x660 fs/ext4/inode.c:816
 ext4_get_block_unwritten+0x2a/0x40 fs/ext4/inode.c:847
 ext4_block_write_begin+0x5ea/0x12a0 fs/ext4/inode.c:1101
 ext4_write_begin+0x6bc/0x13d0
 ext4_da_write_begin+0x4a2/0xc30 fs/ext4/inode.c:2987
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+0x7c8/0x7d0 mm/page_alloc.c:3534
 free_unref_page_list+0x14b/0xa60 mm/page_alloc.c:3671
 release_pages+0x1310/0x1370 mm/swap.c:1009
 free_pages_and_swap_cache+0x8a/0xa0 mm/swap_state.c:320
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu mm/mmu_gather.c:247 [inline]
 tlb_finish_mmu+0x177/0x320 mm/mmu_gather.c:338
 exit_mmap+0x40d/0x940 mm/mmap.c:3218
 __mmput+0x95/0x310 kernel/fork.c:1179
 mmput+0x5b/0x170 kernel/fork.c:1202
 exit_mm kernel/exit.c:554 [inline]
 do_exit+0xb9c/0x2ca0 kernel/exit.c:867
 do_group_exit+0x141/0x310 kernel/exit.c:1002
 __do_sys_exit_group kernel/exit.c:1013 [inline]
 __se_sys_exit_group kernel/exit.c:1011 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1011
 x64_sys_call+0x610/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff888123762f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888123762f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888123763000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                            ^
 ffff888123763080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888123763100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
EXT4-fs error (device loop0): __ext4_get_inode_loc:4351: comm syz-executor327: Invalid inode table block 0 in block_group 0
EXT4-fs error (device loop0) in ext4_reserve_inode_write:5831: Corrupt filesystem
EXT4-fs error (device loop0): __ext4_ext_dirty:183: inode #16: comm syz-executor327: mark_inode_dirty error
EXT4-fs error (device loop0): __ext4_get_inode_loc:4351: comm syz-executor327: Invalid inode table block 0 in block_group 0
EXT4-fs error (device loop0) in ext4_reserve_inode_write:5831: Corrupt filesystem
EXT4-fs error (device loop0): ext4_punch_hole:4143: inode #16: comm syz-executor327: mark_inode_dirty error

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/10/08 23:00 android13-5.15-lts 6ddd8fde5711 402f1df0 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: out-of-bounds Read in ext4_ext_remove_space
2023/08/04 22:28 android13-5.15-lts 748fd0d9ca0f cdae481e .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: out-of-bounds Read in ext4_ext_remove_space
2025/03/26 07:15 android13-5.15-lts 7d1f9b5c2ff5 89d30d73 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_ext_remove_space
2023/07/17 12:33 android13-5.15-lts 879959450ec7 35d9ecc5 .config console log report syz [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: out-of-bounds Read in ext4_ext_remove_space
2025/06/19 17:14 android13-5.15-lts e678c93d43cc ed3e87f7 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: use-after-free Write in ext4_ext_remove_space
2025/06/18 07:57 android13-5.15-lts e678c93d43cc e77fae15 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_ext_remove_space
2025/06/18 07:08 android13-5.15-lts e678c93d43cc e77fae15 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: use-after-free Write in ext4_ext_remove_space
2024/07/19 01:37 android13-5.15-lts db06c48ab67e ee4e11c8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: out-of-bounds Read in ext4_ext_remove_space
2024/05/31 09:46 android13-5.15-lts 424f92bcbe8f 0c378259 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: out-of-bounds Read in ext4_ext_remove_space
2023/09/06 00:23 android13-5.15-lts 1317bd27a72f 0b6286dc .config console log report syz [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: out-of-bounds Read in ext4_ext_remove_space
2023/08/04 22:09 android13-5.15-lts 748fd0d9ca0f cdae481e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: out-of-bounds Read in ext4_ext_remove_space
* Struck through repros no longer work on HEAD.