Date:   Thu, 22 Mar 2018 20:29:12 +0000
From:   bugzilla-daemon@...zilla.kernel.org
To:     linux-ext4@...nel.org
Subject: [Bug 199181] New: Out-of-bound access in ext4_valid_block_bitmap
 when mounting and operating on a crafted ext4 image

https://bugzilla.kernel.org/show_bug.cgi?id=199181

            Bug ID: 199181
           Summary: Out-of-bound access in ext4_valid_block_bitmap when
                    mounting and operating on a crafted ext4 image
           Product: File System
           Version: 2.5
    Kernel Version: 4.15.x
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
          Assignee: fs_ext4@...nel-bugs.osdl.org
          Reporter: wen.xu@...ech.edu
        Regression: No

Created attachment 274877
  --> https://bugzilla.kernel.org/attachment.cgi?id=274877&action=edit
The crafted image which causes kernel panic

- Overview
Kernel crashes in ext4_valid_block_bitmap when mounting and operating a crafted
ext4 image

- Reproduce (under root)
# mkdir mnt
# mount -t ext4 230.img mnt
# gcc -o poc poc.c
# ./poc mnt

- Reason
https://elixir.bootlin.com/linux/v4.15/source/fs/ext4/balloc.c#L343

if (!ext4_test_bit(EXT4_B2C(sbi, offset), bh->b_data))
    /* bad block bitmap */
    return blk;

static inline int test_bit_le(int nr, const void *addr)
{
    return test_bit(nr ^ BITOP_LE_SWIZZLE, addr);
}

static inline int test_bit(int nr, const volatile unsigned long *addr)
{
  return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
}

It seems kernel misses boundary check on BIT_WORD(nr), which causes
out-of-bound access on addr (bh->b_data).

- Kernel crash dump
[  262.162847] EXT4-fs (loop0): barriers disabled
[  262.167094] EXT4-fs (loop0): warning: mounting fs with errors, running
e2fsck is recommended
[  262.167268] EXT4-fs (loop0): recovery complete
[  262.167271] EXT4-fs (loop0): mounted filesystem with ordered data mode.
Opts: (null)
[  267.285863] EXT4-fs error (device loop0): ext4_readdir:183: inode #2: comm
poc: path /home/wen/poc/mnt: directory contains a hole at offset 1024
[  267.286057] BUG: unable to handle kernel paging request at ffff8b4bc81dc7f8
[  267.286095] IP: ext4_validate_block_bitmap+0x196/0x350
[  267.286116] PGD 1b13f067 P4D 1b13f067 PUD 0
[  267.286137] Oops: 0000 [#1] SMP PTI
[  267.286160] Modules linked in: vmw_balloon coretemp intel_rapl_perf
input_leds joydev serio_raw snd_ens1371 btusb snd_ac97_codec uvcvideo btrtl
videobuf2_vmalloc btbcm btintel gameport snd_rawmidi videobuf2_memops bluetooth
videobuf2_v4l2 videobuf2_core snd_seq_device ac97_bus snd_pcm videodev media
ecdh_generic snd_timer snd soundcore shpchp mac_hid vmw_vsock_vmci_transport
vsock vmw_vmci sch_fq_codel ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp
libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables x_tables autofs4 btrfs
zstd_compress raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor
async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic usbhid
hid crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc aesni_intel
aes_x86_64 crypto_simd glue_helper cryptd vmwgfx
[  267.286543]  psmouse ttm drm_kms_helper mptspi mptscsih ahci libahci e1000
mptbase scsi_transport_spi syscopyarea sysfillrect sysimgblt fb_sys_fops drm
i2c_piix4 pata_acpi
[  267.286650] CPU: 0 PID: 1344 Comm: poc Not tainted 4.15.0-12-generic
#13-Ubuntu
[  267.286679] Hardware name: VMware, Inc. VMware Virtual Platform/440BX
Desktop Reference Platform, BIOS 6.00 07/02/2015
[  267.286727] RIP: 0010:ext4_validate_block_bitmap+0x196/0x350
[  267.286751] RSP: 0018:ffffb90741703868 EFLAGS: 00010202
[  267.286775] RAX: 000000007ffffffe RBX: ffff8b4bb91a1000 RCX:
0000000000000000
[  267.286833] RDX: ffff8b4bb81dc800 RSI: ffff8b4bb81dc800 RDI:
ffff8b4bb91a1000
[  267.286862] RBP: ffffb907417038b8 R08: ffff8b4bb91a2000 R09:
000000007fffffff
[  267.286889] R10: ffff8b4bb81dc900 R11: ffffb90741703798 R12:
0000000000000000
[  267.286917] R13: ffff8b4bb8e1e2d8 R14: 0000000000000000 R15:
ffff8b4bb91a2000
[  267.286946] FS:  00007fc90862d540(0000) GS:ffff8b4bbc600000(0000)
knlGS:0000000000000000
[  267.286976] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  267.287001] CR2: ffff8b4bc81dc7f8 CR3: 0000000038210006 CR4:
00000000001606f0
[  267.287061] Call Trace:
[  267.287082]  ? ext4_bg_num_gdb+0x7c/0x90
[  267.287106]  ext4_read_block_bitmap_nowait+0xa5/0x5e0
[  267.287129]  ext4_read_block_bitmap+0x19/0x50
[  267.287712]  ext4_free_blocks+0x1f1/0xb60
[  267.288250]  ? _cond_resched+0x19/0x40
[  267.288785]  ? __kmalloc+0x19b/0x220
[  267.289265]  ext4_ext_remove_space+0xb35/0x1200
[  267.289732]  ext4_ext_truncate+0x88/0xa0
[  267.290127]  ext4_truncate+0x363/0x400
[  267.290514]  ext4_setattr+0x95e/0x9d0
[  267.290935]  notify_change+0x2eb/0x440
[  267.291322]  ? ext4_xattr_security_set+0x30/0x30
[  267.291703]  do_truncate+0x73/0xc0
[  267.292071]  path_openat+0xf84/0x16c0
[  267.292426]  ? touch_atime+0x36/0xe0
[  267.292769]  do_filp_open+0x9b/0x110
[  267.293102]  ? __check_object_size+0xaf/0x1b0
[  267.293427]  ? __alloc_fd+0x46/0x170
[  267.293742]  do_sys_open+0x1bb/0x2c0
[  267.294042]  ? do_sys_open+0x1bb/0x2c0
[  267.294332]  ? _cond_resched+0x19/0x40
[  267.294660]  SyS_openat+0x14/0x20
[  267.294941]  do_syscall_64+0x73/0x130
[  267.295208]  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[  267.295472] RIP: 0033:0x7fc90812ec8e
[  267.295723] RSP: 002b:00007ffc8c52e940 EFLAGS: 00000246 ORIG_RAX:
0000000000000101
[  267.295979] RAX: ffffffffffffffda RBX: 0000000000000000 RCX:
00007fc90812ec8e
[  267.296237] RDX: 0000000000000202 RSI: 000055ed620a42d0 RDI:
00000000ffffff9c
[  267.296495] RBP: 00007ffc8c52eb10 R08: 0000000000000003 R09:
0000000000000000
[  267.296754] R10: 0000000000000000 R11: 0000000000000246 R12:
000055ed61d01d30
[  267.297010] R13: 00007ffc8c52ec10 R14: 0000000000000000 R15:
0000000000000000
[  267.297267] Code: 10 48 8b 75 d0 4c 89 45 b8 48 01 d0 48 89 45 c8 e8 d0 dc
04 00 4c 8b 45 b8 49 89 c1 2b 45 c8 49 8b 55 28 41 8b 48 54 d3 f8 48 98 <48> 0f
a3 02 72 7b 4d 85 c9 0f 84 62 ff ff ff 48 8b 83 08 04 00
[  267.298075] RIP: ext4_validate_block_bitmap+0x196/0x350 RSP:
ffffb90741703868
[  267.298347] CR2: ffff8b4bc81dc7f8
[  267.298613] ---[ end trace 1ecf08f3cdf242f0 ]--- 

Reported by Wen Xu from SSlab, Gatech

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