cpufreq: pcc: fix use-after-free and double free in _OSC evaluation

pcc_cpufreq_do_osc() calls acpi_evaluate_object() twice for the
two-phase _OSC negotiation. Between the two calls it freed
output.pointer but left output.length unchanged. Since
acpi_evaluate_object() treats a non-zero length with a non-NULL
pointer as an existing buffer to write into, the second call wrote
into freed memory (use-after-free). The subsequent kfree(output.pointer)
at out_free then freed the same pointer a second time (double free).

Reset output.pointer to NULL and output.length to ACPI_ALLOCATE_BUFFER
after freeing the first result, so ACPICA allocates a fresh buffer for
each phase independently.

Fixes: 0f1d683fb35d ("[CPUFREQ] Processor Clocking Control interface driver")
Signed-off-by: Yuho Choi <dbgh9129@gmail.com>
Reviewed-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Cc: All applicable <stable@vger.kernel.org>
Link: https://patch.msgid.link/20260416144621.93964-1-dbgh9129@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/pcc-cpufreq.c b/drivers/cpufreq/pcc-cpufreq.c
index ac2e90a65f0c4b547d6bd3a280eb75b4debc2d68..a355ec4f3dd4cd04e5542c8547804a0b8c7917b8 100644 (file)
--- a/drivers/cpufreq/pcc-cpufreq.c
+++ b/drivers/cpufreq/pcc-cpufreq.c
@@ -352,6 +352,8 @@ static int __init pcc_cpufreq_do_osc(acpi_handle *handle)
        }
 
        kfree(output.pointer);
+       output.pointer = NULL;
+       output.length = ACPI_ALLOCATE_BUFFER;
        capabilities[0] = 0x0;
        capabilities[1] = 0x1;