linux-kernel - Forwarded: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in extAlloc (2)

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Message-ID: <68d8a379.a00a0220.102ee.0023.GAE@google.com>
Date: Sat, 27 Sep 2025 19:54:49 -0700
From: syzbot <syzbot+13e8cd4926977f8337b6@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Forwarded: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in extAlloc (2)

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***

Subject: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in extAlloc (2)
Author: xandfury@...il.com

syzbot <syzbot+13e8cd4926977f8337b6@...kaller.appspotmail.com> writes:

> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    9221b2819b8a Add linux-next specific files for 20240503
> git tree:       linux-next
> console+strace: <https://syzkaller.appspot.com/x/log.txt?x=14631754980000>
> kernel config:  <https://syzkaller.appspot.com/x/.config?x=8ab537f51a6a0d98>
> dashboard link: <https://syzkaller.appspot.com/bug?extid=13e8cd4926977f8337b6>
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      <https://syzkaller.appspot.com/x/repro.syz?x=15123b1f180000>
> C reproducer:   <https://syzkaller.appspot.com/x/repro.c?x=16b7da2f180000>
>
> Downloadable assets:
> disk image: <https://storage.googleapis.com/syzbot-assets/3e67dbdc3c37/disk-9221b281.raw.xz>
> vmlinux: <https://storage.googleapis.com/syzbot-assets/ade618fa19f8/vmlinux-9221b281.xz>
> kernel image: <https://storage.googleapis.com/syzbot-assets/df12e5073c97/bzImage-9221b281.xz>
> mounted in repro: <https://storage.googleapis.com/syzbot-assets/41dea5c977c2/mount_0.gz>
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+13e8cd4926977f8337b6@...kaller.appspotmail.com
>
> loop0: detected capacity change from 0 to 32768
> ————[ cut here ]————
> UBSAN: shift-out-of-bounds in fs/jfs/jfs_extent.c:319:16
> shift exponent 108 is too large for 64-bit type ’s64’ (aka ’long long’)
> CPU: 0 PID: 5090 Comm: syz-executor421 Not tainted 6.9.0-rc6-next-20240503-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
> 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_shift_out_of_bounds+0x3c8/0x420 lib/ubsan.c:468
>  extBalloc fs/jfs/jfs_extent.c:319 [inline]
>  extAlloc+0xe5c/0x1010 fs/jfs/jfs_extent.c:122
>  jfs_get_block+0x41b/0xe60 fs/jfs/inode.c:248
>  __block_write_begin_int+0x50c/0x1a70 fs/buffer.c:2128
>  __block_write_begin fs/buffer.c:2177 [inline]
>  block_write_begin+0x9b/0x1e0 fs/buffer.c:2236
>  jfs_write_begin+0x31/0x70 fs/jfs/inode.c:299
>  generic_perform_write+0x322/0x640 mm/filemap.c:4016
>  generic_file_write_iter+0xaf/0x310 mm/filemap.c:4137
>  new_sync_write fs/read_write.c:497 [inline]
>  vfs_write+0xa72/0xc90 fs/read_write.c:590
>  ksys_write+0x1a0/0x2c0 fs/read_write.c:643
>  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: 0033:0x7f4d15f6f639
> 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:00007fff3dae85f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007fff3dae87c8 RCX: 00007f4d15f6f639
> RDX: 00000000fffffef2 RSI: 0000000020000240 RDI: 0000000000000004
> RBP: 00007f4d15fe8610 R08: 0000000000000000 R09: 00007fff3dae87c8
> R10: 0000000000006162 R11: 0000000000000246 R12: 0000000000000001
> R13: 00007fff3dae87b8 R14: 0000000000000001 R15: 0000000000000001
>  </TASK>
> —[ end trace ]—
>
>
> —
> This report is generated by a bot. It may contain errors.
> See <https://goo.gl/tpsmEJ> for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> <https://goo.gl/tpsmEJ#status> for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report’s subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
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#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master