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ACPI: CPPC: Fix NULL pointer dereference when nosmp is used

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With nosmp in cmdline, other CPUs are not brought up, leaving
their cpc_desc_ptr NULL. CPU0's iteration via for_each_possible_cpu()
dereferences these NULL pointers, causing panic.

Panic backtrace:

[    0.401123] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000b8
...
[    0.403255] [<ffffffff809a5818>] cppc_allow_fast_switch+0x6a/0xd4
...
Kernel panic - not syncing: Attempted to kill init!

Fixes: 3cc30dd00a ("cpufreq: CPPC: Enable fast_switch")
Reported-by: Xu Lu <[email protected]>
Signed-off-by: Yunhui Cui <[email protected]>
Link: https://patch.msgid.link/[email protected]
[ rjw: New subject ]
Signed-off-by: Rafael J. Wysocki <[email protected]>
This commit is contained in:
Yunhui Cui authored and Rafael J. Wysocki committed 2025-06-10 20:52:50 +02:00
1 parent 19272b37aa
commit 15eece6c5b
1 file changed
+1 -1
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drivers/acpi/cppc_acpi.c
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@@ -476,7 +476,7 @@ bool cppc_allow_fast_switch(void)
struct cpc_desc *cpc_ptr;
int cpu;
for_each_possible_cpu(cpu) {
for_each_present_cpu(cpu) {
cpc_ptr = per_cpu(cpc_desc_ptr, cpu);
desired_reg = &cpc_ptr->cpc_regs[DESIRED_PERF];
if (!CPC_IN_SYSTEM_MEMORY(desired_reg) &&