Date:   Thu, 22 Mar 2018 21:06:17 +0000
From:   bugzilla-daemon@...zilla.kernel.org
To:     linux-ext4@...nel.org
Subject: [Bug 199185] New: Invalid pointer reference in get_acl
 (fs/posix_acl.c) when mounting and operating crafted ext4 image

https://bugzilla.kernel.org/show_bug.cgi?id=199185

            Bug ID: 199185
           Summary: Invalid pointer reference in get_acl (fs/posix_acl.c)
                    when mounting and operating 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 274887
  --> https://bugzilla.kernel.org/attachment.cgi?id=274887&action=edit
The crafted image which causes kernel panic

- Overview
Kernel references invalid pointer when mounting and later operating on a
crafted ext4 image

- Reproduce
# mkdir mnt
# mount -t ext4 136.img mnt
# gcc -o poc poc.c
# ./poc ./mnt

- Reason
https://elixir.bootlin.com/linux/v4.15/source/fs/posix_acl.c#L154

acl = inode->i_op->get_acl(inode, type);

if (IS_ERR(acl)) {
      /*
       * Remove our sentinel so that we don't block future attempts
       * to cache the ACL.
       */
      cmpxchg(p, sentinel, ACL_NOT_CACHED);
      return acl;
}

Interestingly, it seems ext4's get_acl can return 0xffffffffc0c0c0c0, which
also bypasses the check `if (IS_ERR(acl))`.

- Kernel dump
[  740.268286] EXT4-fs (loop0): warning: mounting unchecked fs, running e2fsck
is recommended
[  740.268788] EXT4-fs (loop0): mounted filesystem without journal. Opts:
(null)
[  750.149045] EXT4-fs error (device loop0): ext4_readdir:238: inode #2: block
44: comm poc: path /home/wen/data/ext4-kernel/20180311/get_acl/mnt: bad entry
in directory: inode out of bounds - offset=12(12), inode=4294901762,
rec_len=12, name_len=2
[  750.166268] EXT4-fs error (device loop0): mb_free_blocks:1468: group 0,
inode 16: block 1985:freeing already freed block (bit 1984); block bitmap
corrupt.
[  750.166342] EXT4-fs error (device loop0): ext4_mb_generate_buddy:756: group
0, block bitmap and bg descriptor inconsistent: 960 vs 961 free clusters
[  750.166525] BUG: unable to handle kernel paging request at ffffffffc0c0c0c0
[  750.166641] IP: get_acl+0x90/0x100
[  750.166687] PGD 1aa0e067 P4D 1aa0e067 PUD 1aa10067 PMD 0
[  750.166717] Oops: 0002 [#1] SMP PTI
[  750.166793] 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
[  750.167360]  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
[  750.167462] CPU: 0 PID: 1322 Comm: poc Not tainted 4.15.0-12-generic
#13-Ubuntu
[  750.167538] Hardware name: VMware, Inc. VMware Virtual Platform/440BX
Desktop Reference Platform, BIOS 6.00 07/02/2015
[  750.167636] RIP: 0010:get_acl+0x90/0x100
[  750.167683] RSP: 0018:ffffb90740d27d18 EFLAGS: 00010286
[  750.167708] RAX: ffffffffc0c0c0c0 RBX: ffffffffc0c0c0c0 RCX:
0000000000000000
[  750.167793] RDX: 0000000000000001 RSI: ffff8b4bb91e8c20 RDI:
0000000000000000
[  750.167847] RBP: ffffb90740d27d40 R08: 000000000002be00 R09:
ffffffffa64ddca2
[  750.167900] R10: ffff8b4bb8df8ea0 R11: 007a0000007a6162 R12:
ffff8b4bb8e277e8
[  750.167927] R13: ffff8b4bb6401701 R14: 0000000000008000 R15:
ffff8b4bb8e277f8
[  750.167955] FS:  00007fa818f7c540(0000) GS:ffff8b4bbc600000(0000)
knlGS:0000000000000000
[  750.168011] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  750.168868] CR2: ffffffffc0c0c0c0 CR3: 00000000391ee005 CR4:
00000000001606f0
[  750.169437] Call Trace:
[  750.169944]  posix_acl_chmod+0x51/0xf0
[  750.170435]  ext4_setattr+0x1f2/0x9d0
[  750.170925]  ? filename_lookup+0xf2/0x190
[  750.171379]  notify_change+0x2eb/0x440
[  750.171826]  chmod_common+0x16a/0x180
[  750.172516]  SyS_chmod+0x59/0xb0
[  750.173215]  do_syscall_64+0x73/0x130
[  750.173902]  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
[  750.174531] RIP: 0033:0x7fa818a7dac7
[  750.175097] RSP: 002b:00007ffd57657478 EFLAGS: 00000207 ORIG_RAX:
000000000000005a
[  750.175644] RAX: ffffffffffffffda RBX: 0000000000000000 RCX:
00007fa818a7dac7
[  750.176178] RDX: 00007ffd576574d0 RSI: 0000000000000000 RDI:
0000558df83702f0
[  750.176713] RBP: 00007ffd576575e0 R08: 0000000000000003 R09:
0000000000000000
[  750.177219] R10: ffffffffffffdc2b R11: 0000000000000207 R12:
0000558df6212d30
[  750.177719] R13: 00007ffd576576e0 R14: 0000000000000000 R15:
0000000000000000
[  750.178157] Code: b1 2f 49 8b 44 24 20 48 8b 40 18 48 85 c0 74 40 44 89 f6
4c 89 e7 e8 30 43 92 00 48 3d 00 f0 ff ff 48 89 c3 77 55 48 85 c0 74 03 <3e> ff
00 4c 89 e8 3e 49 0f b1 1f 49 39 c5 75 26 48 89 d8 5b 41
[  750.179468] RIP: get_acl+0x90/0x100 RSP: ffffb90740d27d18
[  750.179889] CR2: ffffffffc0c0c0c0
[  750.180295] ---[ end trace 1ecf08f3cdf242f0 ]---

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