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Johan Hovold 18e6f30276 USB: cdc-acm: fix unthrottle races 
commit 764478f411 upstream.

Fix two long-standing bugs which could potentially lead to memory
corruption or leave the port throttled until it is reopened (on weakly
ordered systems), respectively, when read-URB completion races with
unthrottle().

First, the URB must not be marked as free before processing is complete
to prevent it from being submitted by unthrottle() on another CPU.

	CPU 1				CPU 2
	================		================
	complete()			unthrottle()
	  process_urb();
	  smp_mb__before_atomic();
	  set_bit(i, free);		  if (test_and_clear_bit(i, free))
						  submit_urb();

Second, the URB must be marked as free before checking the throttled
flag to prevent unthrottle() on another CPU from failing to observe that
the URB needs to be submitted if complete() sees that the throttled flag
is set.

	CPU 1				CPU 2
	================		================
	complete()			unthrottle()
	  set_bit(i, free);		  throttled = 0;
	  smp_mb__after_atomic();	  smp_mb();
	  if (throttled)		  if (test_and_clear_bit(i, free))
		  return;			  submit_urb();

Note that test_and_clear_bit() only implies barriers when the test is
successful. To handle the case where the URB is still in use an explicit
barrier needs to be added to unthrottle() for the second race condition.

Also note that the first race was fixed by 36e59e0d70 ("cdc-acm: fix
race between callback and unthrottle") back in 2015, but the bug was
reintroduced a year later.

Fixes: 1aba579f3c ("cdc-acm: handle read pipe errors")
Fixes: 088c64f812 ("USB: cdc-acm: re-write read processing")
Signed-off-by: Johan Hovold <johan@kernel.org>
Acked-by: Oliver Neukum <oneukum@suse.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-10 17:54:10 +02:00
arch perf/x86/intel: Initialize TFA MSR 2019-05-10 17:54:08 +02:00
block block: pass no-op callback to INIT_WORK(). 2019-05-08 07:21:51 +02:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: x86/poly1305 - fix overflow during partial reduction 2019-04-27 09:36:37 +02:00
Documentation USB: core: Fix bug caused by duplicate interface PM usage counter 2019-05-08 07:21:44 +02:00
drivers USB: cdc-acm: fix unthrottle races 2019-05-10 17:54:10 +02:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock 2019-05-08 07:21:51 +02:00
include linux/kernel.h: Use parentheses around argument in u64_to_user_ptr() 2019-05-10 17:54:08 +02:00
init Revert "mm: use early_pfn_to_nid in page_ext_init" 2019-03-23 20:09:46 +01:00
ipc ipc/shm.c: use ERR_CAST() for shm_lock() error return 2018-10-05 16:32:04 -07:00
kernel genirq: Prevent use-after-free and work list corruption 2019-05-10 17:54:10 +02:00
lib ubsan: Fix nasty -Wbuiltin-declaration-mismatch GCC-9 warnings 2019-05-10 17:54:04 +02:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm slab: fix a crash by reading /proc/slab_allocators 2019-05-10 17:54:08 +02:00
net mac80211: Honor SW_CRYPTO_CONTROL for unicast keys in AP VLAN mode 2019-05-08 07:21:54 +02:00
samples samples: mei: use /dev/mei0 instead of /dev/mei 2019-02-15 08:10:11 +01:00
scripts fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock 2019-05-08 07:21:51 +02:00
security selinux: never allow relabeling on context mounts 2019-05-08 07:21:54 +02:00
sound ASoC: Intel: kbl: fix wrong number of channels 2019-05-10 17:54:09 +02:00
tools objtool: Add rewind_stack_do_exit() to the noreturn list 2019-05-10 17:54:08 +02:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: arm/arm64: vgic-its: Take the srcu lock when parsing the memslots 2019-05-04 09:20:14 +02:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS platform/x86: Add Intel AtomISP2 dummy / power-management driver 2019-04-20 09:16:02 +02:00
Makefile Linux 4.19.41 2019-05-08 07:21:55 +02:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -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.
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.