Shm segments can be marked for lazy destruction via shmctl(IPC_RMID),
which destroys a segment once it is no longer attached to any
processes. We were unconditionally decrementing the segment refcount
on shmctl(IPC_RMID) which allowed a user to force a segment to be
destroyed by repeatedly calling shmctl(IPC_RMID), with outstanding
memory maps to the segment.
This is problematic because the memory released by a segment destroyed
this way can be reused by a different process while remaining
accessible by the process with outstanding maps to the segment.
PiperOrigin-RevId: 219713660
Change-Id: I443ab838322b4fb418ed87b2722c3413ead21845
Attempting to create a zero-len shm segment causes a panic since we
try to allocate a zero-len filemem region. The existing code had a
guard to disallow this, but the check didn't encode the fact that
requesting a private segment implies a segment creation regardless of
whether IPC_CREAT is explicitly specified.
PiperOrigin-RevId: 218405743
Change-Id: I30aef1232b2125ebba50333a73352c2f907977da
We have been unnecessarily creating too many savable types implicitly.
PiperOrigin-RevId: 206334201
Change-Id: Idc5a3a14bfb7ee125c4f2bb2b1c53164e46f29a8
Rahat Mahmood
Ian Gudger
Brian Geffon
Zhaozhong Ni
Michael Pratt