[PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore

[Eric W. Biederman]

Recently syzbot reported[0] that there is a deadlock amongst the users
of exec_update_mutex.

The simplest and most robust solution appears to be making
exec_update_mutex a read/write lock and having everything execept for
exec take the lock for read.

This set of changes upgrades rwsem so it has the functionality needed
and uses a rw_semaphore to replace the current mutex.

Eric W. Biederman (3):
      rwsem: Implement down_read_killable_nested
      rwsem: Implement down_read_interruptible
      exec: Transform exec_update_mutex into a rw_semaphore

 fs/exec.c                    | 12 ++++++------
 fs/proc/base.c               | 10 +++++-----
 include/linux/rwsem.h        |  3 +++
 include/linux/sched/signal.h | 11 ++++++-----
 init/init_task.c             |  2 +-
 kernel/events/core.c         | 12 ++++++------
 kernel/fork.c                |  6 +++---
 kernel/kcmp.c                | 30 +++++++++++++++---------------
 kernel/locking/rwsem.c       | 40 ++++++++++++++++++++++++++++++++++++++++
 kernel/pid.c                 |  4 ++--
 10 files changed, 87 insertions(+), 43 deletions(-)

[0] https://lkml.kernel.org/r/00000000000063640c05ade8e3de@xxxxxxxxxx

Eric