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Filename Latest commit message Latest commit date
Xiaochen Shen d0c4c5a89f x86/resctrl: Remove superfluous kernfs_get() calls to prevent refcount leak
commit fd8d9db3559a29fd737bcdb7c4fcbe1940caae34 upstream.

Willem reported growing of kernfs_node_cache entries in slabtop when
repeatedly creating and removing resctrl subdirectories as well as when
repeatedly mounting and unmounting the resctrl filesystem.

On resource group (control as well as monitoring) creation via a mkdir
an extra kernfs_node reference is obtained to ensure that the rdtgroup
structure remains accessible for the rdtgroup_kn_unlock() calls where it
is removed on deletion. The kernfs_node reference count is dropped by
kernfs_put() in rdtgroup_kn_unlock().

With the above explaining the need for one kernfs_get()/kernfs_put()
pair in resctrl there are more places where a kernfs_node reference is
obtained without a corresponding release. The excessive amount of
reference count on kernfs nodes will never be dropped to 0 and the
kernfs nodes will never be freed in the call paths of rmdir and umount.
It leads to reference count leak and kernfs_node_cache memory leak.

Remove the superfluous kernfs_get() calls and expand the existing
comments surrounding the remaining kernfs_get()/kernfs_put() pair that
remains in use.

Superfluous kernfs_get() calls are removed from two areas:

  (1) In call paths of mount and mkdir, when kernfs nodes for "info",
  "mon_groups" and "mon_data" directories and sub-directories are
  created, the reference count of newly created kernfs node is set to 1.
  But after kernfs_create_dir() returns, superfluous kernfs_get() are
  called to take an additional reference.

  (2) kernfs_get() calls in rmdir call paths.

Fixes: 17eafd0762 ("x86/intel_rdt: Split resource group removal in two")
Fixes: 4af4a88e0c ("x86/intel_rdt/cqm: Add mount,umount support")
Fixes: f3cbeacaa0 ("x86/intel_rdt/cqm: Add rmdir support")
Fixes: d89b737901 ("x86/intel_rdt/cqm: Add mon_data")
Fixes: c7d9aac613 ("x86/intel_rdt/cqm: Add mkdir support for RDT monitoring")
Fixes: 5dc1d5c6ba ("x86/intel_rdt: Simplify info and base file lists")
Fixes: 60cf5e101f ("x86/intel_rdt: Add mkdir to resctrl file system")
Fixes: 4e978d06de ("x86/intel_rdt: Add "info" files to resctrl file system")
Reported-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Xiaochen Shen <xiaochen.shen@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Willem de Bruijn <willemb@google.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1604085053-31639-1-git-send-email-xiaochen.shen@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-12-02 08:49:55 +01:00
arch x86/resctrl: Remove superfluous kernfs_get() calls to prevent refcount leak 2020-12-02 08:49:55 +01:00
block blk-cgroup: Pre-allocate tree node on blkg_conf_prep 2020-11-10 12:37:30 +01:00
certs
crypto crypto: algif_skcipher - EBUSY on aio should be an error 2020-10-29 09:57:30 +01:00
Documentation xtensa: fix TLBTEMP area placement 2020-11-24 13:29:22 +01:00
drivers irqchip/exiu: Fix the index of fwspec for IRQ type 2020-12-02 08:49:55 +01:00
fs efivarfs: revert "fix memory leak in efivarfs_create()" 2020-12-02 08:49:53 +01:00
include arch: pgtable: define MAX_POSSIBLE_PHYSMEM_BITS where needed 2020-12-02 08:49:50 +01:00
init printk: reduce LOG_BUF_SHIFT range for H8300 2020-11-05 11:43:16 +01:00
ipc
kernel sched/fair: Fix overutilized update in enqueue_task_fair() 2020-11-24 13:29:24 +01:00
lib random32: make prandom_u32() output unpredictable 2020-11-18 19:20:20 +01:00
LICENSES
mm mm, page_alloc: skip ->waternark_boost for atomic order-0 allocations 2020-11-24 13:29:24 +01:00
net batman-adv: set .owner to THIS_MODULE 2020-12-02 08:49:50 +01:00
samples samples/bpf: Fix possible deadlock in xdpsock 2020-11-05 11:43:17 +01:00
scripts scripts/setlocalversion: make git describe output more reliable 2020-11-01 12:01:01 +01:00
security selinux: Fix error return code in sel_ib_pkey_sid_slow() 2020-11-18 19:20:30 +01:00
sound ALSA: hda/realtek: Add some Clove SSID in the ALC293(ALC1220) 2020-11-24 13:29:20 +01:00
tools perf probe: Fix to die_entrypc() returns error correctly 2020-12-02 08:49:54 +01:00
usr
virt KVM: arm64: vgic-v3: Drop the reporting of GICR_TYPER.Last for userspace 2020-12-02 08:49:46 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile Linux 5.4.80 2020-11-24 13:29:24 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.