RE: [PATCH] EDAC/Intel: Fix shift-out-of-bounds when DIMM/NVDIMM is absent

[Zhuo, Qiuxu]

> From: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> ...
> Subject: [PATCH] EDAC/Intel: Fix shift-out-of-bounds when DIMM/NVDIMM
> is absent
> 
> The following splat can be found on many systems equipped with EDAC:
> [   13.875276] UBSAN: shift-out-of-bounds in
> drivers/edac/skx_common.c:369:16
> [   13.875279] shift exponent -66 is negative
> [   13.875280] CPU: 11 PID: 519 Comm: systemd-udevd Not tainted 6.4.0-rc1+
> #1
> [   13.875282] Hardware name: HP HP Z4 G5 Workstation Desktop PC/8962,
> BIOS U61 Ver. 01.01.15 04/19/2023
> [   13.875283] Call Trace:
> [   13.875285]  <TASK>
> [   13.875287]  dump_stack_lvl+0x48/0x70
> [   13.875295]  dump_stack+0x10/0x20
> [   13.875297]  __ubsan_handle_shift_out_of_bounds+0x156/0x310
> [   13.875302]  ? __kmem_cache_alloc_node+0x196/0x300
> [   13.875307]  skx_get_dimm_info.cold+0xac/0x15d [i10nm_edac]
> [   13.875312]  i10nm_get_dimm_config+0x240/0x360 [i10nm_edac]
> [   13.875316]  ? kasprintf+0x4e/0x80
> [   13.875321]  skx_register_mci+0x12b/0x1d0 [i10nm_edac]
> [   13.875324]  ? __pfx_i10nm_get_dimm_config+0x10/0x10 [i10nm_edac]
> [   13.875329]  i10nm_init+0x89f/0x1d10 [i10nm_edac]
> [   13.875333]  ? __pfx_i10nm_init+0x10/0x10 [i10nm_edac]
> [   13.875337]  do_one_initcall+0x46/0x240
> [   13.875342]  ? kmalloc_trace+0x2a/0xb0
> [   13.875346]  do_init_module+0x6a/0x280
> [   13.875350]  load_module+0x2419/0x2500
> [   13.875353]  ? security_kernel_post_read_file+0x5c/0x80
> [   13.875358]  __do_sys_finit_module+0xcc/0x150
> [   13.875360]  ? __do_sys_finit_module+0xcc/0x150
> [   13.875363]  __x64_sys_finit_module+0x18/0x30
> [   13.875365]  do_syscall_64+0x59/0x90
> [   13.875368]  ? syscall_exit_to_user_mode+0x2a/0x50
> [   13.875371]  ? do_syscall_64+0x69/0x90
> [   13.875372]  ? do_syscall_64+0x69/0x90
> [   13.875373]  ? do_syscall_64+0x69/0x90
> [   13.875374]  ? do_syscall_64+0x69/0x90
> [   13.875375]  ? syscall_exit_to_user_mode+0x2a/0x50
> [   13.875376]  ? do_syscall_64+0x69/0x90
> [   13.875377]  ? do_syscall_64+0x69/0x90
> [   13.875378]  ? do_syscall_64+0x69/0x90
> [   13.875379]  ? sysvec_call_function+0x4e/0xb0
> [   13.875381]  entry_SYSCALL_64_after_hwframe+0x72/0xdc
> 
> When a DIMM slot is empty, the read value of mtr can be 0xffffffff, therefore

Looked like a buggy BIOS/hw that didn't set the mtr register.

1. Did you print the mtr register whose value was 0xffffffff?
2. Can you take a dmesg log with kernel "CONFIG_EDAC_DEBUG=y" enabled?
3. What was the CPU? Please take the output of "lscpu". 
4. Did you verify your patch that the issue was fixed on your systems?

Thanks!
-Qiuxu

> the wrong "ranks" value creates shift-out-of-bounds error. The same issue
> can be found on NVDIMM too.
> 
> So only consider DIMM/NVDIMM is present when the value of
> mtr/mcddrtcfg is not ~0.
> ...