[PATCH 5.19 057/717] riscv: Make VM_WRITE imply VM_READ

[Greg Kroah-Hartman]

From: Andrew Bresticker <abrestic@xxxxxxxxxxxx>

commit 7ab72c597356be1e7f0f3d856e54ce78527f43c8 upstream.

RISC-V does not presently have write-only mappings as that PTE bit pattern
is considered reserved in the privileged spec, so allow handling of read
faults in VMAs that have VM_WRITE without VM_READ in order to be consistent
with other architectures that have similar limitations.

Fixes: 2139619bcad7 ("riscv: mmap with PROT_WRITE but no PROT_READ is invalid")
Reviewed-by: Atish Patra <atishp@xxxxxxxxxxxx>
Signed-off-by: Andrew Bresticker <abrestic@xxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20220915193702.2201018-2-abrestic@xxxxxxxxxxxx/
Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/riscv/mm/fault.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -184,7 +184,8 @@ static inline bool access_error(unsigned
 		}
 		break;
 	case EXC_LOAD_PAGE_FAULT:
-		if (!(vma->vm_flags & VM_READ)) {
+		/* Write implies read */
+		if (!(vma->vm_flags & (VM_READ | VM_WRITE))) {
 			return true;
 		}
 		break;