From: Todd Poynor <toddpoynor@google.com>
Date: Wed, 5 Feb 2014 00:08:37 +0000 (-0800)
Subject: staging: ashmem: Avoid deadlock between read and mmap calls
X-Git-Tag: v3.14-rc3~12^2~31
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=077f6db9731673753ca41a5c3acbb5ead142658a;p=pandora-kernel.git

staging: ashmem: Avoid deadlock between read and mmap calls

Avoid holding ashmem_mutex across code that can page fault.  Page faults
grab the mmap_sem for the process, which are also held by mmap calls
prior to calling ashmem_mmap, which locks ashmem_mutex.  The reversed
order of locking between the two can deadlock.

The calls that can page fault are read() and the ASHMEM_SET_NAME and
ASHMEM_GET_NAME ioctls.  Move the code that accesses userspace pages
outside the ashmem_mutex.

Cc: Colin Cross <ccross@android.com>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
[jstultz: minor commit message tweaks]
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

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