Subject: CVE-2022-48647: sfc: fix TX channel offset when using legacy interrupts

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

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

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

sfc: fix TX channel offset when using legacy interrupts

In legacy interrupt mode the tx_channel_offset was hardcoded to 1, but
that's not correct if efx_sepparate_tx_channels is false. In that case,
the offset is 0 because the tx queues are in the single existing channel
at index 0, together with the rx queue.

Without this fix, as soon as you try to send any traffic, it tries to
get the tx queues from an uninitialized channel getting these errors:
  WARNING: CPU: 1 PID: 0 at drivers/net/ethernet/sfc/tx.c:540 efx_hard_start_xmit+0x12e/0x170 [sfc]
  [...]
  RIP: 0010:efx_hard_start_xmit+0x12e/0x170 [sfc]
  [...]
  Call Trace:
   <IRQ>
   dev_hard_start_xmit+0xd7/0x230
   sch_direct_xmit+0x9f/0x360
   __dev_queue_xmit+0x890/0xa40
  [...]
  BUG: unable to handle kernel NULL pointer dereference at 0000000000000020
  [...]
  RIP: 0010:efx_hard_start_xmit+0x153/0x170 [sfc]
  [...]
  Call Trace:
   <IRQ>
   dev_hard_start_xmit+0xd7/0x230
   sch_direct_xmit+0x9f/0x360
   __dev_queue_xmit+0x890/0xa40
  [...]

The Linux kernel CVE team has assigned CVE-2022-48647 to this issue.

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

	Issue introduced in 5.10.122 with commit bf2af9b24313 and fixed in 5.10.146 with commit b4afd3878f96
	Issue introduced in 5.15.47 with commit 06cb7e134f8f and fixed in 5.15.71 with commit 360910b88d14
	Issue introduced in 5.19 with commit c308dfd1b43e and fixed in 5.19.12 with commit 5f623a77cfc2
	Issue introduced in 5.19 with commit c308dfd1b43e and fixed in 6.0 with commit f232af429565
	Issue introduced in 5.17.15 with commit 1a7c0b3ef93d
	Issue introduced in 5.18.4 with commit b2d60329a0b8

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-2022-48647
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/ethernet/sfc/efx_channels.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/b4afd3878f961d3517f27b3213730fceef77945c
	https://git.kernel.org/stable/c/360910b88d1466a90644a4e0533803b594344a2b
	https://git.kernel.org/stable/c/5f623a77cfc2d501d72bcb4f9ee71721e6c766ff
	https://git.kernel.org/stable/c/f232af4295653afa4ade3230462b3be15ad16419