Subject: CVE-2024-35852: mlxsw: spectrum_acl_tcam: Fix memory leak when canceling rehash work

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

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

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

mlxsw: spectrum_acl_tcam: Fix memory leak when canceling rehash work

The rehash delayed work is rescheduled with a delay if the number of
credits at end of the work is not negative as supposedly it means that
the migration ended. Otherwise, it is rescheduled immediately.

After "mlxsw: spectrum_acl_tcam: Fix possible use-after-free during
rehash" the above is no longer accurate as a non-negative number of
credits is no longer indicative of the migration being done. It can also
happen if the work encountered an error in which case the migration will
resume the next time the work is scheduled.

The significance of the above is that it is possible for the work to be
pending and associated with hints that were allocated when the migration
started. This leads to the hints being leaked [1] when the work is
canceled while pending as part of ACL region dismantle.

Fix by freeing the hints if hints are associated with a work that was
canceled while pending.

Blame the original commit since the reliance on not having a pending
work associated with hints is fragile.

[1]
unreferenced object 0xffff88810e7c3000 (size 256):
  comm "kworker/0:16", pid 176, jiffies 4295460353
  hex dump (first 32 bytes):
    00 30 95 11 81 88 ff ff 61 00 00 00 00 00 00 80  .0......a.......
    00 00 61 00 40 00 00 00 00 00 00 00 04 00 00 00  ..a.@...........
  backtrace (crc 2544ddb9):
    [<00000000cf8cfab3>] kmalloc_trace+0x23f/0x2a0
    [<000000004d9a1ad9>] objagg_hints_get+0x42/0x390
    [<000000000b143cf3>] mlxsw_sp_acl_erp_rehash_hints_get+0xca/0x400
    [<0000000059bdb60a>] mlxsw_sp_acl_tcam_vregion_rehash_work+0x868/0x1160
    [<00000000e81fd734>] process_one_work+0x59c/0xf20
    [<00000000ceee9e81>] worker_thread+0x799/0x12c0
    [<00000000bda6fe39>] kthread+0x246/0x300
    [<0000000070056d23>] ret_from_fork+0x34/0x70
    [<00000000dea2b93e>] ret_from_fork_asm+0x1a/0x30

The Linux kernel CVE team has assigned CVE-2024-35852 to this issue.

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

	Issue introduced in 5.1 with commit c9c9af91f1d9 and fixed in 5.4.275 with commit 51cefc9da400
	Issue introduced in 5.1 with commit c9c9af91f1d9 and fixed in 5.10.216 with commit 857ed800133f
	Issue introduced in 5.1 with commit c9c9af91f1d9 and fixed in 5.15.158 with commit 63d814d93c5c
	Issue introduced in 5.1 with commit c9c9af91f1d9 and fixed in 6.1.90 with commit 5bfe7bf9656e
	Issue introduced in 5.1 with commit c9c9af91f1d9 and fixed in 6.6.30 with commit de1aaefa75be
	Issue introduced in 5.1 with commit c9c9af91f1d9 and fixed in 6.8.9 with commit d72dd6fcd788
	Issue introduced in 5.1 with commit c9c9af91f1d9 and fixed in 6.9 with commit fb4e2b70a719

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-2024-35852
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/mlxsw/spectrum_acl_tcam.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/51cefc9da400b953fee749c9e5d26cd4a2b5d758
	https://git.kernel.org/stable/c/857ed800133ffcfcee28582090b63b0cbb8ba59d
	https://git.kernel.org/stable/c/63d814d93c5cce4c18284adc810028f28dca493f
	https://git.kernel.org/stable/c/5bfe7bf9656ed2633718388f12b7c38b86414a04
	https://git.kernel.org/stable/c/de1aaefa75be9d0ec19c9a3e0e2f9696de20c6ab
	https://git.kernel.org/stable/c/d72dd6fcd7886d0523afbab8b4a4b22d17addd7d
	https://git.kernel.org/stable/c/fb4e2b70a7194b209fc7320bbf33b375f7114bd5