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Douglas Anderson d9962b0d42 r8152: Block future register access if register access fails
Even though the functions to read/write registers can fail, most of
the places in the r8152 driver that read/write register values don't
check error codes. The lack of error code checking is problematic in
at least two ways.

The first problem is that the r8152 driver often uses code patterns
similar to this:
  x = read_register()
  x = x | SOME_BIT;
  write_register(x);

...with the above pattern, if the read_register() fails and returns
garbage then we'll end up trying to write modified garbage back to the
Realtek adapter. If the write_register() succeeds that's bad. Note
that as of commit f53a7ad189 ("r8152: Set memory to all 0xFFs on
failed reg reads") the "garbage" returned by read_register() will at
least be consistent garbage, but it is still garbage.

It turns out that this problem is very serious. Writing garbage to
some of the hardware registers on the Ethernet adapter can put the
adapter in such a bad state that it needs to be power cycled (fully
unplugged and plugged in again) before it can enumerate again.

The second problem is that the r8152 driver generally has functions
that are long sequences of register writes. Assuming everything will
be OK if a random register write fails in the middle isn't a great
assumption.

One might wonder if the above two problems are real. You could ask if
we would really have a successful write after a failed read. It turns
out that the answer appears to be "yes, this can happen". In fact,
we've seen at least two distinct failure modes where this happens.

On a sc7180-trogdor Chromebook if you drop into kdb for a while and
then resume, you can see:
1. We get a "Tx timeout"
2. The "Tx timeout" queues up a USB reset.
3. In rtl8152_pre_reset() we try to reinit the hardware.
4. The first several (2-9) register accesses fail with a timeout, then
   things recover.

The above test case was actually fixed by the patch ("r8152: Increase
USB control msg timeout to 5000ms as per spec") but at least shows
that we really can see successful calls after failed ones.

On a different (AMD) based Chromebook with a particular adapter, we
found that during reboot tests we'd also sometimes get a transitory
failure. In this case we saw -EPIPE being returned sometimes. Retrying
worked, but retrying is not always safe for all register accesses
since reading/writing some registers might have side effects (like
registers that clear on read).

Let's fully lock out all register access if a register access fails.
When we do this, we'll try to queue up a USB reset and try to unlock
register access after the reset. This is slightly tricker than it
sounds since the r8152 driver has an optimized reset sequence that
only works reliably after probe happens. In order to handle this, we
avoid the optimized reset if probe didn't finish. Instead, we simply
retry the probe routine in this case.

When locking out access, we'll use the existing infrastructure that
the driver was using when it detected we were unplugged. This keeps us
from getting stuck in delay loops in some parts of the driver.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2023-10-22 11:46:18 +01:00
arch LoongArch fixes for v6.6-rc7 2023-10-19 11:02:28 -07:00
block block: Don't invalidate pagecache for invalid falloc modes 2023-10-11 15:53:17 -06:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto crypto: sm2 - Fix crash caused by uninitialized context 2023-09-20 13:10:10 +08:00
Documentation Including fixes from bluetooth, netfilter, WiFi. 2023-10-19 12:08:18 -07:00
drivers r8152: Block future register access if register access fails 2023-10-22 11:46:18 +01:00
fs v6.6-rc7.vfs.fixes 2023-10-19 09:37:41 -07:00
include Including fixes from bluetooth, netfilter, WiFi. 2023-10-19 12:08:18 -07:00
init workqueue: Changes for v6.6 2023-09-01 16:06:32 -07:00
io_uring io-wq: fully initialize wqe before calling cpuhp_state_add_instance_nocalls() 2023-10-05 14:11:18 -06:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel v6.6-rc7.vfs.fixes 2023-10-19 09:37:41 -07:00
lib maple_tree: add MAS_UNDERFLOW and MAS_OVERFLOW states 2023-09-29 17:20:46 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: slab: Do not create kmalloc caches smaller than arch_slab_minalign() 2023-10-11 15:24:49 +02:00
net neighbour: fix various data-races 2023-10-20 17:41:29 -07:00
rust Documentation work keeps chugging along; stuff for 6.6 includes: 2023-08-30 20:05:42 -07:00
samples VFIO updates for v6.6-rc1 2023-08-30 20:36:01 -07:00
scripts kbuild: remove stale code for 'source' symlink in packaging scripts 2023-10-01 23:06:06 +09:00
security KEYS: trusted: Remove redundant static calls usage 2023-10-10 11:19:43 -07:00
sound TTY/Serial driver fixes for 6.6-rc6 2023-10-15 09:11:39 -07:00
tools Including fixes from bluetooth, netfilter, WiFi. 2023-10-19 12:08:18 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap MAINTAINERS: update Matthieu's email address 2023-10-05 09:34:32 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Char/Misc driver fixes for 6.6-rc6 2023-10-15 09:07:27 -07:00
Makefile Linux 6.6-rc6 2023-10-15 13:34:39 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.