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kernfs: fix memleak in kernel_ops_readdir()

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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>
This commit is contained in:
Andrea Arcangeli 2019-08-05 10:34:04 -07:00 committed by Greg Kroah-Hartman
parent ac43432cb1
commit cc798c8389
1 changed files with 5 additions and 2 deletions
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7
fs/kernfs/dir.c
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@ -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;