lib: sbi: check result of pmp_get() in is_pmp_entry_mapped()

pmp_get() may return an error if the given entry, given by the caller
of is_pmp_entry_mapped(), is invalid. This results in the output
parameters for pmp_get() being uninitialized. To avoid using garbage
values, check the result and return early if necessary.

This issue is not being hit because at the moment
is_pmp_entry_mapped() is only being called from a single site with a
valid hardcoded value.

Signed-off-by: Carlos López <[email protected]>
Reviewed-by: Anup Patel <[email protected]>

lib/sbi/riscv_asm.c

@@ -291,7 +291,8 @@ int is_pmp_entry_mapped(unsigned long entry)
 	unsigned long addr;
 	unsigned long log2len;
 
-	pmp_get(entry, &prot, &addr, &log2len);
+	if (pmp_get(entry, &prot, &addr, &log2len) != 0)
+		return false;
 
 	/* If address matching bits are non-zero, the entry is enable */
 	if (prot & PMP_A)