UBSAN: array-index-out-of-bounds in decompress_lznt

Status: fixed on 2026/07/15 08:27
Subsystems: ntfs3
[Documentation on labels]
Reported-by: syzbot+39b2fb0f2638669008ec@syzkaller.appspotmail.com
Fix commit: 7160a57192fb ntfs3: fix out-of-bounds read in decompress_lznt
First crash: 805d, last: 680d
Cause bisection: introduced by (bisect log) :
commit d68968440b1a75dee05cfac7f368f1aa139e1911
Author: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Date: Mon Jan 29 07:30:09 2024 +0000

  fs/ntfs3: Update inode->i_size after success write into compressed file

Crash: UBSAN: array-index-out-of-bounds in decompress_lznt (log)
Repro: C syz .config
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ ✨ AI Jobs (6)
ID Workflow Result Correct Bug Created Started Finished Revision Error
a027ecef assessment-security 💥 UBSAN: array-index-out-of-bounds in decompress_lznt 2026/07/05 00:23 2026/07/05 00:23 2026/07/05 00:45 93f57954 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/22b2b3f29046598a15...
truncated to first 200 bytes; open job for full error
9739a353 assessment-security 💥 UBSAN: array-index-out-of-bounds in decompress_lznt 2026/06/18 00:17 2026/06/18 00:17 2026/06/18 00:41 b62b3ded 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/22b2b3f29046598a15...
truncated to first 200 bytes; open job for full error
33f2b557 assessment-security 💥 UBSAN: array-index-out-of-bounds in decompress_lznt 2026/06/09 19:50 2026/06/09 19:50 2026/06/09 20:16 c36c07f6 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/22b2b3f29046598a15...
truncated to first 200 bytes; open job for full error
db8bd237 assessment-security 💥 UBSAN: array-index-out-of-bounds in decompress_lznt 2026/06/02 20:12 2026/06/02 20:12 2026/06/02 20:36 62fe1528 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/22b2b3f29046598a15...
truncated to first 200 bytes; open job for full error
da8e5c54 assessment-security 💥 UBSAN: array-index-out-of-bounds in decompress_lznt 2026/05/30 04:07 2026/05/30 04:07 2026/05/30 04:34 6b4a8443 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/22b2b3f29046598a15...
truncated to first 200 bytes; open job for full error
5ebf19dd assessment-security 💥 UBSAN: array-index-out-of-bounds in decompress_lznt 2026/05/13 04:05 2026/05/13 04:05 2026/05/13 04:35 ac1aeadb 
failed to run ["make" "KERNELVERSION=syzkaller" "KERNELRELEASE=syzkaller" "LOCALVERSION=-syzkaller" "-j" "32" "ARCH=x86_64" "CC=ccache clang" "LD=ld.lld" "O=/app/workdir/cache/build/22b2b3f29046598a15...
truncated to first 200 bytes; open job for full error
▶ ▼ Discussions (3)
Title Replies (including bot) Last reply
[PATCH] ntfs3: fix out-of-bounds read in decompress_lznt 2 (2) 2026/04/30 12:00
[syzbot] [ntfs3?] UBSAN: array-index-out-of-bounds in decompress_lznt 0 (5) 2026/04/17 16:20
[PATCH] ntfs3: check if more than chunk-size bytes are written 1 (2) 2024/05/15 12:59
▶ ▼ Last patch testing requests (13)
Created Duration User Patch Repo Result
2026/04/17 16:20 14m tristmd@gmail.com patch https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master report log
2026/04/17 10:12 13m tristmd@gmail.com patch https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master report log
2026/02/25 01:13 53m retest repro upstream report log
2025/12/16 22:09 32m retest repro upstream report log
2025/10/07 03:04 16m retest repro upstream report log
2025/07/27 20:41 13m retest repro upstream report log
2025/05/18 18:01 16m retest repro upstream report log
2025/03/08 18:00 13m retest repro upstream report log
2024/12/28 16:06 14m retest repro upstream report log
2024/08/23 16:04 14m almaz.alexandrovich@paragon-software.com https://github.com/Paragon-Software-Group/linux-ntfs3.git master report log
2024/07/01 21:55 11m mukattreyee@gmail.com https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master report log
2024/05/25 02:23 11m retest repro upstream report log
2024/05/15 12:40 17m andrewjballance@gmail.com patch upstream OK log
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2024/10/15 02:04 0m bisect fix upstream error job log
2024/09/12 15:49 2h15m bisect fix upstream OK (0) job log log
2024/08/10 20:02 1h14m bisect fix upstream OK (0) job log log
2024/06/29 15:14 1h07m bisect fix upstream OK (0) job log log

Sample crash report:
------------[ cut here ]------------
UBSAN: array-index-out-of-bounds in fs/ntfs3/lznt.c:240:16
index 9 is out of range for type 'const size_t[9]' (aka 'const unsigned long[9]')
CPU: 1 PID: 5072 Comm: syz-executor335 Not tainted 6.9.0-rc7-syzkaller-00136-gf4345f05c0df #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
 ubsan_epilogue lib/ubsan.c:231 [inline]
 __ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429
 decompress_chunk fs/ntfs3/lznt.c:240 [inline]
 decompress_lznt+0x229/0xd50 fs/ntfs3/lznt.c:387
 ni_read_frame+0x1633/0x1c50 fs/ntfs3/frecord.c:2684
 ni_readpage_cmpr+0x38b/0xa60 fs/ntfs3/frecord.c:2143
 ntfs_read_folio+0x19e/0x210 fs/ntfs3/inode.c:725
 filemap_read_folio+0x1a0/0x790 mm/filemap.c:2331
 filemap_update_page mm/filemap.c:2415 [inline]
 filemap_get_pages+0x15a9/0x2090 mm/filemap.c:2529
 filemap_read+0x457/0xfa0 mm/filemap.c:2601
 __kernel_read+0x5c8/0xab0 fs/read_write.c:434
 integrity_kernel_read+0xb0/0x100 security/integrity/iint.c:28
 ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:485 [inline]
 ima_calc_file_shash security/integrity/ima/ima_crypto.c:516 [inline]
 ima_calc_file_hash+0xadb/0x1b30 security/integrity/ima/ima_crypto.c:573
 ima_collect_measurement+0x535/0xa90 security/integrity/ima/ima_api.c:291
 process_measurement+0x13ac/0x1f60 security/integrity/ima/ima_main.c:359
 ima_file_check+0xf2/0x170 security/integrity/ima/ima_main.c:559
 security_file_post_open+0x6d/0xa0 security/security.c:2981
 do_open fs/namei.c:3644 [inline]
 path_openat+0x28b7/0x3240 fs/namei.c:3799
 do_filp_open+0x235/0x490 fs/namei.c:3826
 do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
 do_sys_open fs/open.c:1421 [inline]
 __do_sys_open fs/open.c:1429 [inline]
 __se_sys_open fs/open.c:1425 [inline]
 __x64_sys_open+0x225/0x270 fs/open.c:1425
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbd0c2059b9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffa3c72cd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007fffa3c72ea8 RCX: 00007fbd0c2059b9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000180
RBP: 00007fbd0c298610 R08: 00007fffa3c72ea8 R09: 00007fffa3c72ea8
R10: 00007fffa3c72ea8 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fffa3c72e98 R14: 0000000000000001 R15: 0000000000000001
 </TASK>
---[ end trace ]---

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/05/11 01:53 upstream f4345f05c0df f7c35481 .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci2-upstream-fs UBSAN: array-index-out-of-bounds in decompress_lznt
2024/05/11 01:31 upstream f4345f05c0df f7c35481 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs UBSAN: array-index-out-of-bounds in decompress_lznt
* Struck through repros no longer work on HEAD.