linux-kernel - [syzbot] [ext4?] UBSAN: shift-out-of-bounds in ext2_fill

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Message-ID: <00000000000079134b05fdf78048@google.com>
Date:   Mon, 12 Jun 2023 16:58:57 -0700
From:   syzbot <syzbot+af5e10f73dbff48f70af@...kaller.appspotmail.com>
To:     adilger.kernel@...ger.ca, jack@...e.com,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        tytso@....edu
Subject: [syzbot] [ext4?] UBSAN: shift-out-of-bounds in ext2_fill_super (2)

Hello,

syzbot found the following issue on:

HEAD commit:    908f31f2a05b Merge branch 'for-next/core', remote-tracking..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=124e9053280000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c1058fe68f4b7b2c
dashboard link: https://syzkaller.appspot.com/bug?extid=af5e10f73dbff48f70af
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=10f66595280000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14abde43280000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/87d095820229/disk-908f31f2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a1bf67af9675/vmlinux-908f31f2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7784a88b37e8/Image-908f31f2.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/2816e591e0fa/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+af5e10f73dbff48f70af@...kaller.appspotmail.com

memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=5969 'syz-executor354'
loop0: detected capacity change from 0 to 512
EXT2-fs (loop0): (no)user_xattr optionsnot supported
================================================================================
UBSAN: shift-out-of-bounds in fs/ext2/super.c:1015:40
shift exponent 63 is too large for 32-bit type 'int'
CPU: 0 PID: 5969 Comm: syz-executor354 Not tainted 6.4.0-rc4-syzkaller-g908f31f2a05b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:233
 show_stack+0x2c/0x44 arch/arm64/kernel/stacktrace.c:240
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
 dump_stack+0x1c/0x28 lib/dump_stack.c:113
 ubsan_epilogue lib/ubsan.c:217 [inline]
 __ubsan_handle_shift_out_of_bounds+0x2f4/0x36c lib/ubsan.c:387
 ext2_fill_super+0x2270/0x2450 fs/ext2/super.c:1015
 mount_bdev+0x274/0x370 fs/super.c:1380
 ext2_mount+0x44/0x58 fs/ext2/super.c:1491
 legacy_get_tree+0xd4/0x16c fs/fs_context.c:610
 vfs_get_tree+0x90/0x274 fs/super.c:1510
 do_new_mount+0x25c/0x8c4 fs/namespace.c:3039
 path_mount+0x590/0xe04 fs/namespace.c:3369
 do_mount fs/namespace.c:3382 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount fs/namespace.c:3568 [inline]
 __arm64_sys_mount+0x45c/0x594 fs/namespace.c:3568
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2c0 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x244 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x64/0x198 arch/arm64/kernel/syscall.c:191
 el0_svc+0x4c/0x160 arch/arm64/kernel/entry-common.c:647
 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:665
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591
================================================================================
EXT2-fs (loop0): error: can't find an ext2 filesystem on dev loop0.

---
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