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

syzbot
2025-09-28T02:54:50Z

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

syzbot <syzbot+13e8cd4926977f8337b6@syzkaller.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@syzkaller.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.
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#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master