mlxsw: spectrum_buffers: Fix memory corruptions on Spectrum-4 systems

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

mlxsw: spectrum_buffers: Fix memory corruptions on Spectrum-4 systems

The following two shared buffer operations make use of the Shared Buffer Status Register (SBSR):

# devlink sb occupancy snapshot pci/0000:01:00.0 # devlink sb occupancy clearmax pci/0000:01:00.0

The register has two masks of 256 bits to denote on which ingress / egress ports the register should operate on. Spectrum-4 has more than 256 ports, so the register was extended by cited commit with a new 'port_page' field.

However, when filling the register's payload, the driver specifies the ports as absolute numbers and not relative to the first port of the port page, resulting in memory corruptions [1].

Fix by specifying the ports relative to the first port of the port page.

[1] BUG: KASAN: slab-use-after-free in mlxsw_sp_sb_occ_snapshot+0xb6d/0xbc0 Read of size 1 at addr ffff8881068cb00f by task devlink/1566 [...] Call Trace:

dump_stack_lvl+0xc6/0x120 print_report+0xce/0x670 kasan_report+0xd7/0x110 mlxsw_sp_sb_occ_snapshot+0xb6d/0xbc0 mlxsw_devlink_sb_occ_snapshot+0x75/0xb0 devlink_nl_sb_occ_snapshot_doit+0x1f9/0x2a0 genl_family_rcv_msg_doit+0x20c/0x300 genl_rcv_msg+0x567/0x800 netlink_rcv_skb+0x170/0x450 genl_rcv+0x2d/0x40 netlink_unicast+0x547/0x830 netlink_sendmsg+0x8d4/0xdb0 __sys_sendto+0x49b/0x510 __x64_sys_sendto+0xe5/0x1c0 do_syscall_64+0xc1/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f [...] Allocated by task 1: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 __kasan_kmalloc+0x8f/0xa0 copy_verifier_state+0xbc2/0xfb0 do_check_common+0x2c51/0xc7e0 bpf_check+0x5107/0x9960 bpf_prog_load+0xf0e/0x2690 __sys_bpf+0x1a61/0x49d0 __x64_sys_bpf+0x7d/0xc0 do_syscall_64+0xc1/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 1: kasan_save_stack+0x33/0x60 kasan_save_track+0x14/0x30 kasan_save_free_info+0x3b/0x60 poison_slab_object+0x109/0x170 __kasan_slab_free+0x14/0x30 kfree+0xca/0x2b0 free_verifier_state+0xce/0x270 do_check_common+0x4828/0xc7e0 bpf_check+0x5107/0x9960 bpf_prog_load+0xf0e/0x2690 __sys_bpf+0x1a61/0x49d0 __x64_sys_bpf+0x7d/0xc0 do_syscall_64+0xc1/0x1d0 entry_SYSCALL_64_after_hwframe+0x77/0x7f