CVE-2024-26586

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

mlxsw: spectrumacltcam: 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: mlxswspacltcamgroupupdate+0x116/0x120 [...] dumpstack_lvl+0x36/0x50 panic+0x305/0x330 __stackchkfail+0x15/0x20 mlxswspacltcamgroupupdate+0x116/0x120 mlxswspacltcamgroupregionattach+0x69/0x110 mlxswspacltcamvchunkget+0x492/0xa20 mlxswspacltcamventryadd+0x25/0xe0 mlxswspaclruleadd+0x47/0x240 mlxswspflowerreplace+0x1a9/0x1d0 tcsetupcbadd+0xdc/0x1c0 flhwreplacefilter+0x146/0x1f0 flchange+0xc17/0x1360 tcnewtfilter+0x472/0xb90 rtnetlinkrcvmsg+0x313/0x3b0 netlinkrcvskb+0x58/0x100 netlinkunicast+0x244/0x390 netlink_sendmsg+0x1e4/0x440 ____sys_sendmsg+0x164/0x260 ___sys_sendmsg+0x9a/0xe0 _syssendmsg+0x7a/0xc0 dosyscall64+0x40/0xe0 entrySYSCALL64afterhwframe+0x63/0x6b