Subject: CVE-2024-36930: spi: fix null pointer dereference within spi_sync

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

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

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

spi: fix null pointer dereference within spi_sync

If spi_sync() is called with the non-empty queue and the same spi_message
is then reused, the complete callback for the message remains set while
the context is cleared, leading to a null pointer dereference when the
callback is invoked from spi_finalize_current_message().

With function inlining disabled, the call stack might look like this:

  _raw_spin_lock_irqsave from complete_with_flags+0x18/0x58
  complete_with_flags from spi_complete+0x8/0xc
  spi_complete from spi_finalize_current_message+0xec/0x184
  spi_finalize_current_message from spi_transfer_one_message+0x2a8/0x474
  spi_transfer_one_message from __spi_pump_transfer_message+0x104/0x230
  __spi_pump_transfer_message from __spi_transfer_message_noqueue+0x30/0xc4
  __spi_transfer_message_noqueue from __spi_sync+0x204/0x248
  __spi_sync from spi_sync+0x24/0x3c
  spi_sync from mcp251xfd_regmap_crc_read+0x124/0x28c [mcp251xfd]
  mcp251xfd_regmap_crc_read [mcp251xfd] from _regmap_raw_read+0xf8/0x154
  _regmap_raw_read from _regmap_bus_read+0x44/0x70
  _regmap_bus_read from _regmap_read+0x60/0xd8
  _regmap_read from regmap_read+0x3c/0x5c
  regmap_read from mcp251xfd_alloc_can_err_skb+0x1c/0x54 [mcp251xfd]
  mcp251xfd_alloc_can_err_skb [mcp251xfd] from mcp251xfd_irq+0x194/0xe70 [mcp251xfd]
  mcp251xfd_irq [mcp251xfd] from irq_thread_fn+0x1c/0x78
  irq_thread_fn from irq_thread+0x118/0x1f4
  irq_thread from kthread+0xd8/0xf4
  kthread from ret_from_fork+0x14/0x28

Fix this by also setting message->complete to NULL when the transfer is
complete.

The Linux kernel CVE team has assigned CVE-2024-36930 to this issue.

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

	Issue introduced in 6.0 with commit ae7d2346dc89 and fixed in 6.1.91 with commit e005d6754e3e
	Issue introduced in 6.0 with commit ae7d2346dc89 and fixed in 6.6.31 with commit a30659f1576d
	Issue introduced in 6.0 with commit ae7d2346dc89 and fixed in 6.8.10 with commit 2070d008cc08
	Issue introduced in 6.0 with commit ae7d2346dc89 and fixed in 6.9 with commit 4756fa529b2f

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-2024-36930
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/spi/spi.c

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/e005d6754e3e440257006795b687c4ad8733b493
	https://git.kernel.org/stable/c/a30659f1576d2c8e62e7426232bb18b885fd951a
	https://git.kernel.org/stable/c/2070d008cc08bff50a58f0f4d30f12d3ebf94c00
	https://git.kernel.org/stable/c/4756fa529b2f12b7cb8f21fe229b0f6f47190829