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Robert Richter 216aa145aa EDAC/mc: Fix use-after-free and memleaks during device removal 
A test kernel with the options DEBUG_TEST_DRIVER_REMOVE, KASAN and
DEBUG_KMEMLEAK set, revealed several issues when removing an mci device:

1) Use-after-free:

On 27.11.19 17:07:33, John Garry wrote:
> [   22.104498] BUG: KASAN: use-after-free in
> edac_remove_sysfs_mci_device+0x148/0x180

The use-after-free is caused by the mci_for_each_dimm() macro called in
edac_remove_sysfs_mci_device(). The iterator was introduced with

  c498afaf7d ("EDAC: Introduce an mci_for_each_dimm() iterator").

The iterator loop calls device_unregister(&dimm->dev), which removes
the sysfs entry of the device, but also frees the dimm struct in
dimm_attr_release(). When incrementing the loop in mci_for_each_dimm(),
the dimm struct is accessed again, after having been freed already.

The fix is to free all the mci device's subsequent dimm and csrow
objects at a later point, in _edac_mc_free(), when the mci device itself
is being freed.

This keeps the data structures intact and the mci device can be
fully used until its removal. The change allows the safe usage of
mci_for_each_dimm() to release dimm devices from sysfs.

2) Memory leaks:

Following memory leaks have been detected:

 # grep edac /sys/kernel/debug/kmemleak | sort | uniq -c
       1     [<000000003c0f58f9>] edac_mc_alloc+0x3bc/0x9d0      # mci->csrows
      16     [<00000000bb932dc0>] edac_mc_alloc+0x49c/0x9d0      # csr->channels
      16     [<00000000e2734dba>] edac_mc_alloc+0x518/0x9d0      # csr->channels[chn]
       1     [<00000000eb040168>] edac_mc_alloc+0x5c8/0x9d0      # mci->dimms
      34     [<00000000ef737c29>] ghes_edac_register+0x1c8/0x3f8 # see edac_mc_alloc()

All leaks are from memory allocated by edac_mc_alloc().

Note: The test above shows that edac_mc_alloc() was called here from
ghes_edac_register(), thus both functions show up in the stack trace
but the module causing the leaks is edac_mc. The comments with the data
structures involved were made manually by analyzing the objdump.

The data structures listed above and created by edac_mc_alloc() are
not properly removed during device removal, which is done in
edac_mc_free().

There are two paths implemented to remove the device depending on device
registration, _edac_mc_free() is called if the device is not registered
and edac_unregister_sysfs() otherwise.

The implemenations differ. For the sysfs case, the mci device removal
lacks the removal of subsequent data structures (csrows, channels,
dimms). This causes the memory leaks (see mci_attr_release()).

 [ bp: Massage commit message. ]

Fixes: c498afaf7d ("EDAC: Introduce an mci_for_each_dimm() iterator")
Fixes: faa2ad09c0 ("edac_mc: edac_mc_free() cannot assume mem_ctl_info is registered in sysfs.")
Fixes: 7a623c0390 ("edac: rewrite the sysfs code to use struct device")
Reported-by: John Garry <john.garry@huawei.com>
Signed-off-by: Robert Richter <rrichter@marvell.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: John Garry <john.garry@huawei.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200212120340.4764-3-rrichter@marvell.com
2020-02-13 13:28:52 +01:00
arch Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
block block-5.6-2020-02-05 2020-02-06 06:15:23 +00:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto treewide: remove redundant IS_ERR() before error code check 2020-02-04 03:05:27 +00:00
Documentation Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
drivers EDAC/mc: Fix use-after-free and memleaks during device removal 2020-02-13 13:28:52 +01:00
fs Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
include fs: New zonefs file system 2020-02-09 15:51:46 -08:00
init Tracing updates: 2020-02-06 07:12:11 +00:00
ipc proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
kernel Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
lib Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-08 13:26:41 -08:00
net Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
samples Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
scripts Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
security Merge branch 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-08 13:26:41 -08:00
sound sound fixes for 5.6-rc1 2020-02-06 14:15:01 +00:00
tools A set of fixes and improvements for the perf subsystem: 2020-02-09 12:04:09 -08:00
usr Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
virt KVM: fix overflow of zero page refcount with ksm running 2020-02-05 15:27:46 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
COPYING
CREDITS open: introduce openat2(2) syscall 2020-01-18 09:19:18 -05:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS fs: New zonefs file system 2020-02-09 15:51:46 -08:00
Makefile Linux 5.6-rc1 2020-02-09 16:08:48 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.