Commit cc798c83 authored Aug 05, 2019 by Andrea Arcangeli Committed by Greg Kroah-Hartman Aug 05, 2019

kernfs: fix memleak in kernel_ops_readdir()



If getdents64 is killed or hits on segfault, it'll leave cgroups
directories in sysfs pinned leaking memory because the kernfs node
won't be freed on rmdir and the parent neither.

Repro:

  # for i in `seq 1000`; do mkdir $i; done
  # rmdir *
  # for i in `seq 1000`; do mkdir $i; done
  # rmdir *

  # for i in `seq 1000`; do while :; do ls $i/ >/dev/null; done & done
  # while :; do killall ls; done

  kernfs_node_cache in /proc/slabinfo keeps going up as expected.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # goes way back to original sysfs days
Link: https://lore.kernel.org/r/20190805173404.GF136335@devbig004.ftw2.facebook.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent ac43432c

fs/kernfs/dir.c

+5 −2

Original line number	Diff line number	Diff line
		@@ -1684,11 +1684,14 @@ static int kernfs_fop_readdir(struct file file, struct dir_context ctx)
		kernfs_get(pos);

		mutex_unlock(&kernfs_mutex);
		if (!dir_emit(ctx, name, len, ino, type))
		return 0;
		if (unlikely(!dir_emit(ctx, name, len, ino, type))) {
		kernfs_put(pos);
		goto out;
		}
		mutex_lock(&kernfs_mutex);
		}
		mutex_unlock(&kernfs_mutex);
		out:
		file->private_data = NULL;
		ctx->pos = INT_MAX;
		return 0;

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