Subject: CVE-2024-41088: can: mcp251xfd: fix infinite loop when xmit fails

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

can: mcp251xfd: fix infinite loop when xmit fails

When the mcp251xfd_start_xmit() function fails, the driver stops
processing messages, and the interrupt routine does not return,
running indefinitely even after killing the running application.

Error messages:
[  441.298819] mcp251xfd spi2.0 can0: ERROR in mcp251xfd_start_xmit: -16
[  441.306498] mcp251xfd spi2.0 can0: Transmit Event FIFO buffer not empty. (seq=0x000017c7, tef_tail=0x000017cf, tef_head=0x000017d0, tx_head=0x000017d3).
... and repeat forever.

The issue can be triggered when multiple devices share the same SPI
interface. And there is concurrent access to the bus.

The problem occurs because tx_ring->head increments even if
mcp251xfd_start_xmit() fails. Consequently, the driver skips one TX
package while still expecting a response in
mcp251xfd_handle_tefif_one().

Resolve the issue by starting a workqueue to write the tx obj
synchronously if err = -EBUSY. In case of another error, decrement
tx_ring->head, remove skb from the echo stack, and drop the message.

[mkl: use more imperative wording in patch description]

The Linux kernel CVE team has assigned CVE-2024-41088 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.10 with commit 55e5b97f003e and fixed in 6.1.97 with commit f926c022ebaa
	Issue introduced in 5.10 with commit 55e5b97f003e and fixed in 6.6.37 with commit 3e72558c1711
	Issue introduced in 5.10 with commit 55e5b97f003e and fixed in 6.9.8 with commit 6c6b4afa59c2
	Issue introduced in 5.10 with commit 55e5b97f003e and fixed in 6.10 with commit d8fb63e46c88

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2024-41088
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
	drivers/net/can/spi/mcp251xfd/mcp251xfd-tx.c
	drivers/net/can/spi/mcp251xfd/mcp251xfd.h

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/f926c022ebaabf7963bebf89a97201d66978a025
	https://git.kernel.org/stable/c/3e72558c1711d524e3150103739ddd06650e291b
	https://git.kernel.org/stable/c/6c6b4afa59c2fb4d1759235f866d8caed2aa4729
	https://git.kernel.org/stable/c/d8fb63e46c884c898a38f061c2330f7729e75510