On Tue, Mar 10, 2020 at 01:52:05PM -0500, Eric W. Biederman wrote:
During exec some file descriptors are closed and the files struct is unshared. But all of that can happen at other times and it has the same protections during exec as at ordinary times. So stop taking the cred_guard_mutex as it is useless.
Furthermore he cred_guard_mutex is a bad idea because it is deadlock prone, as it is held in serveral while waiting possibly indefinitely for userspace to do something.
Cc: Sargun Dhillon sargun@sargun.me Cc: Christian Brauner christian.brauner@ubuntu.com Cc: Arnd Bergmann arnd@arndb.de Fixes: 8649c322f75c ("pid: Implement pidfd_getfd syscall") Signed-off-by: "Eric W. Biederman" ebiederm@xmission.com
kernel/pid.c | 6 ------ 1 file changed, 6 deletions(-)
Christian if you don't have any objections I will take this one through my tree.
Sure. Acked-by: Christian Brauner christian.brauner@ubuntu.com
I tried to figure out why this code path takes the cred_guard_mutex and the archive on lore.kernel.org was not helpful in finding that part of the conversation.
Let me think a little harder and hopefully get back to you with a sensible explanation.