UBSAN: shift-out-of-bounds in ext4_mb

UBSAN: shift-out-of-bounds in ext4_mb_init
Status: upstream: reported C repro on 2021/02/01 09:16
Reported-by: syzbot+a8b4b0c60155e87e9484@syzkaller.appspotmail.com
Fix commit: f91436d55a27 fs/ext4: fix integer overflow in s_log_groups_per_flex
Patched on: [ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-leak ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce ci-upstream-kmsan-gce-386 ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-kcsan-gce ci2-upstream-usb], missing on: [ci-qemu2-arm32]
First crash: 175d, last: 163d

Cause bisection: introduced by (bisect log) :
commit cfd73237722135807967f389bcbda558a60a30d6
Author: Alex Zhuravlev <bzzz@whamcloud.com>
Date: Tue Apr 21 07:54:07 2020 +0000

ext4: add prefetching for block allocation bitmaps

Crash: UBSAN: shift-out-of-bounds in ext4_mb_init (log)
Repro: C syz .config

Patch testing requests:
Created	Duration	User	Patch	Repo	Result
2021/02/03 13:11	18m	snovitoll@gmail.com		https://linux.googlesource.com/linux/kernel/git/torvalds/linux refs/changes/57/8057/1	OK

Sample crash report:

loop0: detected capacity change from 264192 to 0
================================================================================
UBSAN: shift-out-of-bounds in fs/ext4/mballoc.c:2713:24
shift exponent 60 is too large for 32-bit type 'int'
CPU: 1 PID: 8433 Comm: syz-executor484 Not tainted 5.11.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x137/0x1be lib/dump_stack.c:120
 ubsan_epilogue lib/ubsan.c:148 [inline]
 __ubsan_handle_shift_out_of_bounds+0x432/0x4d0 lib/ubsan.c:395
 ext4_mb_init_backend fs/ext4/mballoc.c:2713 [inline]
 ext4_mb_init+0x19bc/0x19f0 fs/ext4/mballoc.c:2898
 ext4_fill_super+0xc2ec/0xfbe0 fs/ext4/super.c:4983
 mount_bdev+0x26c/0x3a0 fs/super.c:1366
 legacy_get_tree+0xea/0x180 fs/fs_context.c:592
 vfs_get_tree+0x86/0x270 fs/super.c:1496
 do_new_mount fs/namespace.c:2881 [inline]
 path_mount+0x17ad/0x2a00 fs/namespace.c:3211
 do_mount fs/namespace.c:3224 [inline]
 __do_sys_mount fs/namespace.c:3432 [inline]
 __se_sys_mount+0x28c/0x320 fs/namespace.c:3409
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x44710a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 fd ad fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 da ad fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007ffc5b95ff48 EFLAGS: 00000206 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007ffc5b95ffa0 RCX: 000000000044710a
RDX: 0000000020000000 RSI: 0000000020000180 RDI: 00007ffc5b95ff60
RBP: 00007ffc5b95ff60 R08: 00007ffc5b95ffa0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000013
R13: 0000000000000004 R14: 0000000000000003 R15: 0000000000000003
================================================================================

Crashes (5):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-kasan-gce-smack-root	2021/01/31 19:42	upstream	6642d600b541	fc9fd31e	.config	log	report	syz	C		UBSAN: shift-out-of-bounds in ext4_mb_init
ci-upstream-kasan-gce-root	2021/02/12 05:05	upstream	291009f656e8	a5f86b15	.config	log	report			info	UBSAN: shift-out-of-bounds in ext4_mb_init
ci-upstream-kasan-gce-smack-root	2021/02/11 23:03	upstream	291009f656e8	a5f86b15	.config	log	report			info	UBSAN: shift-out-of-bounds in ext4_mb_init
ci-upstream-kasan-gce-smack-root	2021/01/31 19:20	upstream	6642d600b541	fc9fd31e	.config	log	report			info	UBSAN: shift-out-of-bounds in ext4_mb_init
ci-upstream-linux-next-kasan-gce-root	2021/02/04 20:35	linux-next	0e2c50f40b7f	42b90a7c	.config	log	report			info	UBSAN: shift-out-of-bounds in ext4_mb_init