Re: [PATCH 18/19] sched/fair: Avoid cache-aware scheduling for memory-heavy processes

[Chen, Yu C]

On 10/15/2025 2:57 PM, kernel test robot wrote:
> Hello,
>
> kernel test robot noticed "UBSAN:array-index-out-of-bounds_in_drivers/base/cacheinfo.c" on:

[snip]

> [   12.549731][   T83] ------------[ cut here ]------------
> [   12.550388][   T83] UBSAN: array-index-out-of-bounds in drivers/base/cacheinfo.c:37:9
> [   12.551060][   T83] index 4294967295 is out of range for type 'unsigned long[8]'
> [   12.551580][   T83] CPU: 0 UID: 0 PID: 83 Comm: systemd-journal Not tainted 6.17.0-rc4-00035-ge8b871200f11 #1 PREEMPTLAZY
> [   12.551585][   T83] Call Trace:
> [   12.551588][   T83]  __dump_stack (lib/dump_stack.c:95)
> [   12.551594][   T83]  dump_stack_lvl (lib/dump_stack.c:123)
> [   12.551601][   T83]  ubsan_epilogue.llvm.16751680356772289369 (lib/dump_stack.c:129 lib/ubsan.c:233)
> [   12.551607][   T83]  __ubsan_handle_out_of_bounds (lib/ubsan.c:?)
> [   12.551621][   T83]  get_cpu_cacheinfo (drivers/base/cacheinfo.c:?)
> [   12.551625][   T83]  exceed_llc_capacity (include/linux/cacheinfo.h:? kernel/sched/fair.c:1256)

Thanks 0day! It seems that for some reason the assignment of curr_cpu = 
task_cpu(p);
was after the check exceed_llc_capacity(), will fix this.

thanks,
Chenyu