Re: [PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore
On Thu, 03 Dec 2020, Linus Torvalds wrote: On Thu, Dec 3, 2020 at 12:10 PM Eric W. Biederman wrote: 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. Looks sane to me. I'd like the locking people to look at the down_read_*() functions, even if they look simple. Adding Waiman and Davidlohr to the cc just in case they would look at that too, since they've worked on that code. rwsem changes look good to me - and 3/3 looks much nicer than the previous alternatives to the deadlock. Acked-by: Davidlohr Bueso
Re: [PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore
On 12/3/20 5:42 PM, Linus Torvalds wrote: On Thu, Dec 3, 2020 at 12:10 PM Eric W. Biederman wrote: 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. Looks sane to me. I'd like the locking people to look at the down_read_*() functions, even if they look simple. Adding Waiman and Davidlohr to the cc just in case they would look at that too, since they've worked on that code. I have looked at patches 1 & 2 on adding down_read_killable_nested() and down_read_interruptible(). They looks good to me. Cheers, Longman
Re: [PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore
On Thu, Dec 3, 2020 at 12:10 PM Eric W. Biederman wrote: > > 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. Looks sane to me. I'd like the locking people to look at the down_read_*() functions, even if they look simple. Adding Waiman and Davidlohr to the cc just in case they would look at that too, since they've worked on that code. Linus
[PATCH 0/3] exec: Transform exec_update_mutex into a rw_semaphore
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/63640c05ade8e...@google.com Eric
