tree ea77b283a68b2b2a5cbcf29706d8c2d6361d18e6
parent bcfb87fb75fa3a9b96c8a73d19166897d167fe3f
author Ming Lei <ming.lei@canonical.com> 1365085357 +0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1365201352 -0700

sysfs: check if one entry has been removed before freeing

It might be a kernel disaster if one sysfs entry is freed but
still referenced by sysfs tree.

Recently Dave and Sasha reported one use-after-free problem on
sysfs entry, and the problem has been troubleshooted with help
of debug message added in this patch.

Given sysfs_get_dirent/sysfs_put are exported APIs, even inside
sysfs they are called in many contexts(kobject/attribe add/delete,
inode init/drop, dentry lookup/release, readdir, ...), it is healthful
to check the removed flag before freeing one entry and dump message
if it is freeing without being removed first.

Cc: Dave Jones <davej@redhat.com>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>