tree e1daaf80162f3a19313bcf46c55ffdb9aed6722a
parent 108bd7e1f3331f69e46bcc5ecd74a28e0b99b39d
author Todd Poynor <toddpoynor@google.com> 1370392178 -0700
committer Todd Poynor <toddpoynor@google.com> 1370633355 -0700

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.

Bug: 9261835
Change-Id: If1322e981d29c889a56cdc9dfcbc6df2729a45e9
Signed-off-by: Todd Poynor <toddpoynor@google.com>