Description: shmem reader can block hole punch indefinitely
References:
Notes:
 jmm> Initial patch (f00cdc6df7d7cfcabb5b740911e6788cb0802bdb) was wrong:
 jmm> https://lkml.org/lkml/2014/7/2/518
 bwh> Hugh says Linux 3.1+ need these fixes but it's not known whether
 bwh> earlier versions do.
Bugs:
upstream: released (3.16-rc7) [f00cdc6df7d7cfcabb5b740911e6788cb0802bdb, 8e205f779d1443a94b5ae81aa359cb535dd3021e, b1a366500bd537b50c3aad26dc7df083ec03a448]
2.6.32-upstream-stable: N/A "Vulnerable code introduced later"
sid: released (3.14.15-1)
3.2-wheezy-security: released (3.2.63-1)
3.16-upstream-stable: N/A
2.6.32-squeeze-security: N/A "Vulnerable code introduced later"
3.2-upstream-stable: released (3.2.62) [shmem-fix-faulting-into-a-hole-while-it-s-punched.patch, shmem-fix-faulting-into-a-hole-not-taking-i_mutex.patch, shmem-fix-splicing-from-a-hole-while-it-s-punched.patch]