riscv: Reset pmm when PR_TAGGED_ADDR_ENABLE is not set

In set_tagged_addr_ctrl(), when PR_TAGGED_ADDR_ENABLE is not set, pmlen
is correctly set to 0, but it forgets to reset pmm. This results in the
CPU pmm state not corresponding to the software pmlen state.

Fix this by resetting pmm along with pmlen.

Fixes: 2e17430 ("riscv: Add support for the tagged address ABI")
Signed-off-by: Zishun Yi <vulab@iscas.ac.cn>
Reviewed-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://patch.msgid.link/20260322160022.21908-1-vulab@iscas.ac.cn
Signed-off-by: Paul Walmsley <pjw@kernel.org>

Author: ISCAS-Vulab

arch/riscv/kernel/process.c

@@ -347,8 +347,10 @@ long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg)
 	if (arg & PR_TAGGED_ADDR_ENABLE && (tagged_addr_disabled || !pmlen))
 		return -EINVAL;
 
-	if (!(arg & PR_TAGGED_ADDR_ENABLE))
+	if (!(arg & PR_TAGGED_ADDR_ENABLE)) {
 		pmlen = PMLEN_0;
+		pmm = ENVCFG_PMM_PMLEN_0;
+	}
 
 	if (mmap_write_lock_killable(mm))
 		return -EINTR;