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Lars Ellenberg 7c752ed325 drbd: fix potential get_ldev/put_ldev refcount imbalance during attach
Race:

drbd_adm_attach()               | async drbd_md_endio()
                                |
device->ldev is still NULL.     |
                                |
drbd_md_read(                   |
 .endio = drbd_md_endio;        |
 submit;                        |
 ....                           |
 wait for done == 1;            |       done = 1;
);                              |       wake_up();
.. lot of other stuff,          |
.. includeing taking and        |
...giving up locks,             |
.. doing further IO,            |
.. stuff that takes "some time" |
                                | while in this context,
                                | this is the next statement.
                                | which means this context was scheduled
.. only then, finally,          | away for "some time".
device->ldev = nbc;             |
                                |       if (device->ldev)
                                |               put_ldev()

Unlikely, but possible. I was able to provoke it "reliably"
by adding an mdelay(500); after the wake_up().
Fixed by moving the if (!NULL) put_ldev() before done = 1;

Impact of the bug was that the resulting refcount imbalance
could lead to premature destruction of the object, potentially
causing a NULL pointer dereference during a subsequent detach.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
History 2017-08-29 15:34:45 -06:00
arch block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
block bsg: remove #if 0'ed code 2017-08-29 10:50:30 -06:00
certs modsign: add markers to endif-statements in certs/Makefile 2017-07-14 11:01:37 +10:00
crypto crypto: authencesn - Fix digest_null crash 2017-07-18 17:01:11 +08:00
Documentation Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-07-28 12:31:49 -07:00
drivers drbd: fix potential get_ldev/put_ldev refcount imbalance during attach 2017-08-29 15:34:45 -06:00
firmware firmware/Makefile: force recompilation if makefile changes 2017-05-08 17:15:10 -07:00
fs block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
include drbd: new disk-option disable-write-same 2017-08-29 15:34:44 -06:00
init random: do not ignore early device randomness 2017-07-12 16:26:00 -07:00
ipc ipc/util.h: update documentation for ipc_getref() and ipc_putref() 2017-07-12 16:26:02 -07:00
kernel block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
lib uuid: fix incorrect uuid_equal conversion in test_uuid_test 2017-07-21 09:38:30 +02:00
mm block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
net NFS client bugfixes for 4.13 2017-07-21 16:26:01 -07:00
samples Merge branch 'akpm' (patches from Andrew) 2017-07-13 12:38:49 -07:00
scripts DeviceTree fixes for 4.13: 2017-07-28 17:21:41 -07:00
security Now that IPC and other changes have landed, enable manual markings for 2017-07-19 08:55:18 -07:00
sound sound fixes for 4.13-rc3 2017-07-27 10:44:28 -07:00
tools tools/kvm_stat: add '-f help' to get the available event list 2017-07-26 19:04:53 +02:00
usr ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk. 2017-07-06 16:24:30 -07:00
virt KVM: make pid available for uevents without debugfs 2017-07-26 18:57:44 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap power supply and reset changes for the v4.12 series (part 2) 2017-05-12 12:02:21 -07:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS avr32: remove support for AVR32 architecture 2017-05-01 09:27:15 +02:00
Kbuild kbuild: Consolidate header generation from ASM offset information 2017-04-13 05:43:37 +09:00
Kconfig kbuild: migrate all arch to the kconfig mainmenu upgrade 2010-09-19 22:54:11 -04:00
MAINTAINERS skd: Update maintainer information 2017-08-18 08:45:29 -06:00
Makefile Linux 4.13-rc2 2017-07-23 16:15:17 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.