From 3d29aefd8e23f96d086b0129745ebab56214e3a3 Mon Sep 17 00:00:00 2001 From: Sukadev Bhattiprolu Date: Wed, 11 Nov 2009 14:26:32 -0800 Subject: [PATCH] pidns: fix a leak in /proc dentries and inodes with pid namespaces. Daniel Lezcano reported a leak in 'struct pid' and 'struct pid_namespace' that is discussed in: http://lkml.org/lkml/2009/10/2/159. To summarize the thread, when container-init is terminated, it sets the PF_EXITING flag, zaps other processes in the container and waits to reap them. As a part of reaping, the container-init should flush any /proc dentries associated with the processes. But because the container-init is itself exiting and the following PF_EXITING check, the dentries are not flushed, resulting in leak in /proc inodes and dentries. This fix reverts the commit cbb96600a49ae0f22 ("Fix /proc dcache deadlock in do_exit") which introduced the check for PF_EXITING. At the time of the commit, shrink_dcache_parent() flushed dentries from other filesystems also and could have caused a deadlock which the commit fixed. But as pointed out by Eric Biederman, after commit 3a40a553a47d4eefb, shrink_dcache_parent() no longer affects other filesystems. So reverting the commit is now safe. As pointed out by Jan Kara, the leak is not as critical since the unclaimed space will be reclaimed under memory pressure or by: echo 3 > /proc/sys/vm/drop_caches But since this check is no longer required, its best to remove it. Signed-off-by: Sukadev Bhattiprolu Reported-by: Daniel Lezcano Acked-by: Eric W. Biederman Acked-by: Jan Kara Cc: Andrea Arcangeli Cc: Serge Hallyn Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/base.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 837469a965984..af643b5aefe89 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2597,8 +2597,7 @@ static void proc_flush_task_mnt(struct vfsmount *mnt, pid_t pid, pid_t tgid) name.len = snprintf(buf, sizeof(buf), "%d", pid); dentry = d_hash_and_lookup(mnt->mnt_root, &name); if (dentry) { - if (!(current->flags & PF_EXITING)) - shrink_dcache_parent(dentry); + shrink_dcache_parent(dentry); d_drop(dentry); dput(dentry); } -- 2.39.5