linux-ext4 - KASAN: use-after-free Write in __ext4_expand_extra

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Date:   Sun, 20 Oct 2019 22:23:08 -0700
From:   syzbot <syzbot+44b6763edfc17144296f@...kaller.appspotmail.com>
To:     adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        tytso@....edu
Subject: KASAN: use-after-free Write in __ext4_expand_extra_isize (2)

Hello,

syzbot found the following crash on:

HEAD commit:    b145b0eb Merge tag 'for-linus' of git://git.kernel.org/pub..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13887f1f600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1ec3be9936e004f6
dashboard link: https://syzkaller.appspot.com/bug?extid=44b6763edfc17144296f
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+44b6763edfc17144296f@...kaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in memset include/linux/string.h:344 [inline]
BUG: KASAN: use-after-free in __ext4_expand_extra_isize+0x1ab/0x290  
fs/ext4/inode.c:5924
Write of size 736 at addr ffff88803763aea0 by task syz-executor.5/28447

CPU: 1 PID: 28447 Comm: syz-executor.5 Not tainted 5.4.0-rc1+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
  __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
  kasan_report+0x12/0x20 mm/kasan/common.c:634
  check_memory_region_inline mm/kasan/generic.c:185 [inline]
  check_memory_region+0x134/0x1a0 mm/kasan/generic.c:192
  memset+0x24/0x40 mm/kasan/common.c:105
  memset include/linux/string.h:344 [inline]
  __ext4_expand_extra_isize+0x1ab/0x290 fs/ext4/inode.c:5924
  ext4_try_to_expand_extra_isize fs/ext4/inode.c:5976 [inline]
  ext4_mark_inode_dirty+0x74e/0x9b0 fs/ext4/inode.c:6052
  ext4_ext_truncate+0x92/0x200 fs/ext4/extents.c:4583
  ext4_truncate+0xc6e/0x13c0 fs/ext4/inode.c:4511
  ext4_evict_inode+0x9d4/0x14e0 fs/ext4/inode.c:289
  evict+0x306/0x680 fs/inode.c:574
  iput_final fs/inode.c:1563 [inline]
  iput+0x55d/0x900 fs/inode.c:1589
  dentry_unlink_inode+0x2d9/0x400 fs/dcache.c:374
  __dentry_kill+0x38b/0x600 fs/dcache.c:579
  dentry_kill fs/dcache.c:698 [inline]
  dput+0x639/0xe10 fs/dcache.c:859
  __fput+0x424/0x890 fs/file_table.c:293
  ____fput+0x16/0x20 fs/file_table.c:313
  task_work_run+0x145/0x1c0 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x904/0x2e60 kernel/exit.c:817
  do_group_exit+0x135/0x360 kernel/exit.c:921
  get_signal+0x47c/0x2500 kernel/signal.c:2734
  do_signal+0x87/0x1700 arch/x86/kernel/signal.c:815
  exit_to_usermode_loop+0x286/0x380 arch/x86/entry/common.c:159
  prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
  do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459a59
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f163d095cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000075c120 RCX: 0000000000459a59
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000075c120
RBP: 000000000075c118 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075c124
R13: 00007ffee9e6c79f R14: 00007f163d0969c0 R15: 000000000075c124

The buggy address belongs to the page:
page:ffffea0000dd8e80 refcount:2 mapcount:0 mapping:ffff8880a2d8e520  
index:0x487
def_blk_aops
flags: 0x1fffc000000203a(referenced|dirty|lru|active|private)
raw: 01fffc000000203a ffffea0000e4cc08 ffffea0000b54b88 ffff8880a2d8e520
raw: 0000000000000487 ffff88808f15d150 00000002ffffffff ffff8880a17cec40
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8880a17cec40

Memory state around the buggy address:
  ffff88803763af00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  ffff88803763af80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff88803763b000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                    ^
  ffff88803763b080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
  ffff88803763b100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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