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Vincent Mailhol 8cdac518ea can: etas_es58x: change opened_channel_cnt's type from atomic_t to u8 
[ Upstream commit f4896248e9 ]

The driver uses an atomic_t variable: struct
es58x_device::opened_channel_cnt to keep track of the number of opened
channels in order to only allocate memory for the URBs when this count
changes from zero to one.

While the intent was to prevent race conditions, the choice of an
atomic_t turns out to be a bad idea for several reasons:

- implementation is incorrect and fails to decrement
  opened_channel_cnt when the URB allocation fails as reported in
  [1].

- even if opened_channel_cnt were to be correctly decremented,
  atomic_t is insufficient to cover edge cases: there can be a race
  condition in which 1/ a first process fails to allocate URBs
  memory 2/ a second process enters es58x_open() before the first
  process does its cleanup and decrements opened_channed_cnt. In
  which case, the second process would successfully return despite
  the URBs memory not being allocated.

- actually, any kind of locking mechanism was useless here because
  it is redundant with the network stack big kernel lock
  (a.k.a. rtnl_lock) which is being hold by all the callers of
  net_device_ops:ndo_open() and net_device_ops:ndo_close(). c.f. the
  ASSERST_RTNL() calls in __dev_open() [2] and __dev_close_many()
  [3].

The atmomic_t is thus replaced by a simple u8 type and the logic to
increment and decrement es58x_device:opened_channel_cnt is simplified
accordingly fixing the bug reported in [1]. We do not check again for
ASSERST_RTNL() as this is already done by the callers.

[1] https://lore.kernel.org/linux-can/20220201140351.GA2548@kili/T/#u
[2] https://elixir.bootlin.com/linux/v5.16/source/net/core/dev.c#L1463
[3] https://elixir.bootlin.com/linux/v5.16/source/net/core/dev.c#L1541

Fixes: 8537257874 ("can: etas_es58x: add core support for ETAS ES58X CAN USB interfaces")
Link: https://lore.kernel.org/all/20220212112713.577957-1-mailhol.vincent@wanadoo.fr
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-03-08 19:12:50 +01:00
arch ARM: tegra: Move panels to AUX bus 2022-03-08 19:12:50 +01:00
block block-map: add __GFP_ZERO flag for alloc_page in function bio_copy_kern 2022-03-08 19:12:31 +01:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: api - Move cryptomgr soft dependency into algapi 2022-02-11 09:10:26 +01:00
Documentation drm/i915/display: Move DRRS code its own file 2022-03-08 19:12:40 +01:00
drivers can: etas_es58x: change opened_channel_cnt's type from atomic_t to u8 2022-03-08 19:12:50 +01:00
fs btrfs: fix ENOSPC failure when attempting direct IO write into NOCOW range 2022-03-08 19:12:46 +01:00
include sched: Fix yet more sched_fork() races 2022-03-08 19:12:49 +01:00
init init: make unknown command line param message clearer 2021-11-18 19:17:11 +01:00
ipc ipc/sem: do not sleep with a spin lock held 2022-02-08 18:34:03 +01:00
kernel sched: Fix yet more sched_fork() races 2022-03-08 19:12:49 +01:00
lib lib/iov_iter: initialize "flags" in new pipe_buffer 2022-02-23 12:03:20 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm memfd: fix F_SEAL_WRITE after shmem huge page allocated 2022-03-08 19:12:48 +01:00
net netfilter: nf_tables: prefer kfree_rcu(ptr, rcu) variant 2022-03-08 19:12:49 +01:00
samples samples: bpf: Fix 'unknown warning group' build warning on Clang 2022-01-27 11:03:29 +01:00
scripts kconfig: fix failing to generate auto.conf 2022-02-23 12:03:20 +01:00
security selinux: fix misuse of mutex_is_locked() 2022-03-02 11:47:48 +01:00
sound ASoC: cs4265: Fix the duplicated control name 2022-03-08 19:12:47 +01:00
tools selftests: mlxsw: tc_police_scale: Make test more robust 2022-03-08 19:12:48 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: s390: Ensure kvm_arch_no_poll() is read once when blocking vCPU 2022-03-08 19:12:34 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS drm fixes for 5.15 final 2021-10-28 12:17:01 -07:00
Makefile Linux 5.15.26 2022-03-02 11:48:10 +01:00
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.