After the process exits, the following three dentries still refer to the pid: /proc/<pid> /proc/<pid>/ns /proc/<pid>/ns/pid https://bugzilla.kernel.org/show_bug.cgi?id=208613 According to the commit f333c700c610 ("pidns: Add a limit on the number of pid namespaces"), if the pid cannot be released, it may result in the inability to create a new pid_ns. Please backport the following patches to the kernel stable trees (from 4.9.y to 5.6.y): 7bc3e6e55acf ("proc: Use a list of inodes to flush from proc") 26dbc60f385f ("proc: Generalize proc_sys_prune_dcache into proc_prune_siblings_dcache") f90f3cafe8d5 ("proc: Use d_invalidate in proc_prune_siblings_dcache") Signed-off-by: Wen Yang <wenyang@xxxxxxxxxxxxxxxxx> Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx
