[PATCH] riscv: Fix kernel crash due to PR_SET_TAGGED_ADDR_CTRL

[Nam Cao]

When userspace does PR_SET_TAGGED_ADDR_CTRL, but Supm extension is not
available, the kernel crashes:

Oops - illegal instruction [#1]
    [snip]
epc : set_tagged_addr_ctrl+0x112/0x15a
 ra : set_tagged_addr_ctrl+0x74/0x15a
epc : ffffffff80011ace ra : ffffffff80011a30 sp : ffffffc60039be10
    [snip]
status: 0000000200000120 badaddr: 0000000010a79073 cause: 0000000000000002
    set_tagged_addr_ctrl+0x112/0x15a
    __riscv_sys_prctl+0x352/0x73c
    do_trap_ecall_u+0x17c/0x20c
    andle_exception+0x150/0x15c

Fix it by checking if Supm is available.

Fixes: 09d6775f503b ("riscv: Add support for userspace pointer masking")
Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
 arch/riscv/kernel/process.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index 7c244de77180..3db2c0c07acd 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -275,6 +275,9 @@ long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg)
 	unsigned long pmm;
 	u8 pmlen;
 
+	if (!riscv_has_extension_unlikely(RISCV_ISA_EXT_SUPM))
+		return -EINVAL;
+
 	if (is_compat_thread(ti))
 		return -EINVAL;
 
-- 
2.39.5