From: Tejun Heo <tj@kernel.org>
Date: Fri, 25 Nov 2011 00:22:24 +0000 (-0500)
Subject: ext4: fix racy use-after-free in ext4_end_io_dio()
X-Git-Tag: v3.2-rc4~10^2
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=4c81f045c0bd2cbb78cc6446a4cd98038fe11a2e

ext4: fix racy use-after-free in ext4_end_io_dio()

ext4_end_io_dio() queues io_end->work and then clears iocb->private;
however, io_end->work calls aio_complete() which frees the iocb
object.  If that slab object gets reallocated, then ext4_end_io_dio()
can end up clearing someone else's iocb->private, this use-after-free
can cause a leak of a struct ext4_io_end_t structure.

Detected and tested with slab poisoning.

[ Note: Can also reproduce using 12 fio's against 12 file systems with the
  following configuration file:

  [global]
  direct=1
  ioengine=libaio
  iodepth=1
  bs=4k
  ba=4k
  size=128m

  [create]
  filename=${TESTDIR}
  rw=write

  -- tytso ]

Google-Bug-Id: 5354697
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: Kent Overstreet <koverstreet@google.com>
Tested-by: Kent Overstreet <koverstreet@google.com>
Cc: stable@kernel.org
---

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