[PATCH -fixes v2] riscv: Fix wrong usage of lm_alias() when splitting a huge linear mapping

[Alexandre Ghiti]

lm_alias() can only be used on kernel mappings since it explicitly uses
__pa_symbol(), so simply fix this by checking where the address belongs
to before.

Fixes: 311cd2f6e253 ("riscv: Fix set_memory_XX() and set_direct_map_XX() by splitting huge linear mappings")
Reported-by: syzbot+afb726d49f84c8d95ee1 at syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-riscv/000000000000620dd0060c02c5e1@google.com/
Signed-off-by: Alexandre Ghiti <alexghiti at rivosinc.com>
---

Changes in v2:
- Fix llvm warning about unitialized return value

 arch/riscv/mm/pageattr.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index fc5fc4f785c4..96cbda683936 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -305,8 +305,13 @@ static int __set_memory(unsigned long addr, int numpages, pgprot_t set_mask,
 				goto unlock;
 		}
 	} else if (is_kernel_mapping(start) || is_linear_mapping(start)) {
-		lm_start = (unsigned long)lm_alias(start);
-		lm_end = (unsigned long)lm_alias(end);
+		if (is_kernel_mapping(start)) {
+			lm_start = (unsigned long)lm_alias(start);
+			lm_end = (unsigned long)lm_alias(end);
+		} else {
+			lm_start = start;
+			lm_end = end;
+		}
 
 		ret = split_linear_mapping(lm_start, lm_end);
 		if (ret)
-- 
2.39.2