Re: [PATCH v2 0/2] Fix NULL pointer dereference issue during discovering UPI topology

["Liang, Kan" <kan.liang@linux.intel.com>]

On 2023-11-27 1:52 p.m., alexander.antonov@linux.intel.com wrote:
> From: Alexander Antonov <alexander.antonov@linux.intel.com>
> 
> The NULL dereference happens inside upi_fill_topology() procedure in
> case of disabling one of the sockets on the system.
> 
> For example, if you disable the 2nd socket on a 4-socket system then
> uncore_max_dies() returns 3 and inside pmu_alloc_topology() memory will
> be allocated only for 3 sockets and stored in type->topology.
> In discover_upi_topology() memory is accessed by socket id from CPUNODEID
> registers which contain physical ids (from 0 to 3) and on the line:
> 
>     upi = &type->topology[nid][idx];
> 
> out-of-bound access will happen and the 'upi' pointer will be passed to
> upi_fill_topology() where it will be dereferenced.
> 
> To avoid this issue update the code to convert physical socket id to
> logical socket id in discover_upi_topology() before accessing memory.
> 
> Changed in v2:
>  1. Factor out topology_gidnid_map() with common code for GIDNIDMAP procedure
> 
> Alexander Antonov (2):
>   perf/x86/intel/uncore: Fix NULL pointer dereference issue in
>     upi_fill_topology()
>   perf/x86/intel/uncore: Factor out topology_gidnid_map()

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>

Thanks,
Kan

> 
>  arch/x86/events/intel/uncore_snbep.c | 71 ++++++++++++++++------------
>  1 file changed, 40 insertions(+), 31 deletions(-)
>