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Mathias Nyman 533b917e06 xhci: dbc: fix bogus 1024 byte prefix if ttyDBC read races with stall event 
commit f3d12ec847 upstream.

DbC may add 1024 bogus bytes to the beginneing of the receiving endpoint
if DbC hw triggers a STALL event before any Transfer Blocks (TRBs) for
incoming data are queued, but driver handles the event after it queued
the TRBs.

This is possible as xHCI DbC hardware may trigger spurious STALL transfer
events even if endpoint is empty. The STALL event contains a pointer
to the stalled TRB, and "remaining" untransferred data length.

As there are no TRBs queued yet the STALL event will just point to first
TRB position of the empty ring, with '0' bytes remaining untransferred.

DbC driver is polling for events, and may not handle the STALL event
before /dev/ttyDBC0 is opened and incoming data TRBs are queued.

The DbC event handler will now assume the first queued TRB (length 1024)
has stalled with '0' bytes remaining untransferred, and copies the data

This race situation can be practically mitigated by making sure the event
handler handles all pending transfer events when DbC reaches configured
state, and only then create dev/ttyDbC0, and start queueing transfers.
The event handler can this way detect the STALL events on empty rings
and discard them before any transfers are queued.

This does in practice solve the issue, but still leaves a small possible
gap for the race to trigger.
We still need a way to distinguish spurious STALLs on empty rings with '0'
bytes remaing, from actual STALL events with all bytes transmitted.

Cc: stable <stable@kernel.org>
Fixes: dfba2174dc ("usb: xhci: Add DbC support in xHCI driver")
Tested-by: Łukasz Bartosik <ukaszb@chromium.org>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-10-29 14:09:00 +01:00
arch riscv: hwprobe: avoid uninitialized variable use in hwprobe_arch_id() 2025-10-29 14:08:59 +01:00
block blk-crypto: fix missing blktrace bio split events 2025-10-19 16:33:48 +02:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: essiv - Check ssize for decryption and in-place encryption 2025-10-19 16:33:42 +02:00
Documentation arm64: errata: Apply workarounds for Neoverse-V3AE 2025-10-23 16:20:47 +02:00
drivers xhci: dbc: fix bogus 1024 byte prefix if ttyDBC read races with stall event 2025-10-29 14:09:00 +01:00
fs ocfs2: clear extent cache after moving/defragmenting extents 2025-10-29 14:08:57 +01:00
include mm/ksm: fix flag-dropping behavior in ksm_madvise 2025-10-23 16:20:47 +02:00
init init: handle bootloader identifier in kernel parameters 2025-10-19 16:33:50 +02:00
io_uring io_uring/sqpoll: be smarter on when to update the stime usage 2025-10-29 14:08:59 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel sched: Remove never used code in mm_cid_get() 2025-10-29 14:08:59 +01:00
lib lib/crypto/curve25519-hacl64: Disable KASAN with clang-17 and older 2025-10-19 16:34:00 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm: prevent poison consumption when splitting THP 2025-10-29 14:08:57 +01:00
net vsock: fix lock inversion in vsock_assign_transport() 2025-10-29 14:08:57 +01:00
rust mm/ksm: fix flag-dropping behavior in ksm_madvise 2025-10-23 16:20:47 +02:00
samples ftrace/samples: Fix function size computation 2025-09-19 16:35:44 +02:00
scripts gcc-plugins: Remove TODO_verify_il for GCC >= 16 2025-10-06 11:17:52 +02:00
security KEYS: trusted_tpm1: Compare HMAC values in constant time 2025-10-19 16:33:51 +02:00
sound ASoC: amd/sdw_utils: avoid NULL deref when devm_kasprintf() fails 2025-10-23 16:20:37 +02:00
tools selftests: mptcp: join: mark implicit tests as skipped if not supported 2025-10-29 14:08:57 +01:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Allow CPU to reschedule while setting per-page memory attributes 2025-07-17 18:37:08 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: give Clippy the minimum supported Rust version 2025-08-01 09:48:44 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.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 MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
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 MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Unbreak 'make tools/*' for user-space targets 2025-10-29 14:08:53 +01:00
README README: Fix spelling 2024-03-18 03:36:32 -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 reStructuredText 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.