Subject: CVE-2021-47199: net/mlx5e: CT, Fix multiple allocations and memleak of mod acts

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

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

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

net/mlx5e: CT, Fix multiple allocations and memleak of mod acts

CT clear action offload adds additional mod hdr actions to the
flow's original mod actions in order to clear the registers which
hold ct_state.
When such flow also includes encap action, a neigh update event
can cause the driver to unoffload the flow and then reoffload it.

Each time this happens, the ct clear handling adds that same set
of mod hdr actions to reset ct_state until the max of mod hdr
actions is reached.

Also the driver never releases the allocated mod hdr actions and
causing a memleak.

Fix above two issues by moving CT clear mod acts allocation
into the parsing actions phase and only use it when offloading the rule.
The release of mod acts will be done in the normal flow_put().

 backtrace:
    [<000000007316e2f3>] krealloc+0x83/0xd0
    [<00000000ef157de1>] mlx5e_mod_hdr_alloc+0x147/0x300 [mlx5_core]
    [<00000000970ce4ae>] mlx5e_tc_match_to_reg_set_and_get_id+0xd7/0x240 [mlx5_core]
    [<0000000067c5fa17>] mlx5e_tc_match_to_reg_set+0xa/0x20 [mlx5_core]
    [<00000000d032eb98>] mlx5_tc_ct_entry_set_registers.isra.0+0x36/0xc0 [mlx5_core]
    [<00000000fd23b869>] mlx5_tc_ct_flow_offload+0x272/0x1f10 [mlx5_core]
    [<000000004fc24acc>] mlx5e_tc_offload_fdb_rules.part.0+0x150/0x620 [mlx5_core]
    [<00000000dc741c17>] mlx5e_tc_encap_flows_add+0x489/0x690 [mlx5_core]
    [<00000000e92e49d7>] mlx5e_rep_update_flows+0x6e4/0x9b0 [mlx5_core]
    [<00000000f60f5602>] mlx5e_rep_neigh_update+0x39a/0x5d0 [mlx5_core]

The Linux kernel CVE team has assigned CVE-2021-47199 to this issue.

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

	Issue introduced in 5.7 with commit 1ef3018f5af3 and fixed in 5.15.5 with commit 486e8de6e233
	Issue introduced in 5.7 with commit 1ef3018f5af3 and fixed in 5.16 with commit 806401c20a0f

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-2021-47199
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/mellanox/mlx5/core/en/tc_ct.c
	drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.h
	drivers/net/ethernet/mellanox/mlx5/core/en_tc.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/486e8de6e233ff2999493533c6259d1cb538653b
	https://git.kernel.org/stable/c/806401c20a0f9c51b6c8fd7035671e6ca841f6c2