Affected: Linux

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

mlxsw: spectrum_acl_tcam: Fix stack corruption

When tc filters are first added to a net device, the corresponding local port gets bound to an ACL group in the device. The group contains a list of ACLs. In turn, each ACL points to a different TCAM region where the filters are stored. During forwarding, the ACLs are sequentially evaluated until a match is found.

One reason to place filters in different regions is when they are added with decreasing priorities and in an alternating order so that two consecutive filters can never fit in the same region because of their key usage.

In Spectrum-2 and newer ASICs the firmware started to report that the maximum number of ACLs in a group is more than 16, but the layout of the register that configures ACL groups (PAGT) was not updated to account for that. It is therefore possible to hit stack corruption [1] in the rare case where more than 16 ACLs in a group are required.

Fix by limiting the maximum ACL group size to the minimum between what the firmware reports and the maximum ACLs that fit in the PAGT register.

Add a test case to make sure the machine does not crash when this condition is hit.

[1] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: mlxsw_sp_acl_tcam_group_update+0x116/0x120 [...] dump_stack_lvl+0x36/0x50 panic+0x305/0x330 __stack_chk_fail+0x15/0x20 mlxsw_sp_acl_tcam_group_update+0x116/0x120 mlxsw_sp_acl_tcam_group_r…

Affected: Ubuntu:20.04:LTS: linux-azure-5.15, Ubuntu:20.04:LTS: linux-azure-fde-5.15, Ubuntu:20.04:LTS: linux-gcp-5.15, Ubuntu:20.04:LTS: linux-gkeop-5.15, Ubuntu:20.04:LTS: linux-hwe-5.15, Ubuntu:20.04:LTS: linux-ibm-5.15, Ubuntu:20.04:LTS: linux-intel-iotg-5.15, Ubuntu:20.04:LTS: linux-lowlatency-hwe-5.15, Ubuntu:20.04:LTS: linux-oracle-5.15, Ubuntu:22.04:LTS: linux and 12 more

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