[PATCH v5 3/3] LoongArch: Avoid initrd overlap during kernel relocation

[WANG Rui]

Validate the relocation address against the initrd region specified via
"initrd=" or "initrdmem=" on the command line. Reject relocation targets
that overlap the initrd to prevent memory corruption during early boot.

Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Co-authored-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Signed-off-by: WANG Rui <r@xxxxxx>
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
---
 arch/loongarch/kernel/relocate.c | 38 ++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
index 0a045964fad5..4b61a9632a98 100644
--- a/arch/loongarch/kernel/relocate.c
+++ b/arch/loongarch/kernel/relocate.c
@@ -222,14 +222,52 @@ static inline void __init *determine_relocation_address(void)
 	return RELOCATED_KASLR(destination);
 }
 
+static unsigned long __init determine_initrd_address(unsigned long *size)
+{
+	unsigned long start = 0;
+	unsigned long key_length;
+	char *p, *endp, *key = "initrd=";
+
+	key_length = strlen(key);
+	p = strstr(boot_command_line, key);
+
+	if (!p) {
+		key = "initrdmem=";
+		key_length = strlen(key);
+		p = strstr(boot_command_line, key);
+	}
+
+	if (p == boot_command_line || (p > boot_command_line && *(p - 1) == ' ')) {
+		p += key_length;
+		start = memparse(p, &endp);
+		if (*endp == ',')
+			*size = memparse(endp + 1, NULL);
+	}
+
+	return start;
+}
+
 static inline int __init relocation_addr_valid(void *location_new)
 {
+	unsigned long kernel_start, kernel_size;
+	unsigned long initrd_start, initrd_size = 0;
+
 	if ((unsigned long)location_new & 0x00000ffff)
 		return 0; /* Inappropriately aligned new location */
 
 	if ((unsigned long)location_new < (unsigned long)_end)
 		return 0; /* New location overlaps original kernel */
 
+	initrd_start = determine_initrd_address(&initrd_size);
+	if (initrd_start && initrd_size) {
+		kernel_start = PHYSADDR(location_new);
+		kernel_size = (unsigned long)_end - (unsigned long)_text;
+
+		if (kernel_start < (initrd_start + initrd_size) &&
+			initrd_start < (kernel_start + kernel_size))
+			return 0; /* initrd/initramfs overlaps kernel */
+	}
+
 	return 1;
 }
 #endif
-- 
2.54.0