[PATCH v2] MIPS: validate DT bootargs before appending them

[Pengpeng Hou]

bootcmdline_scan_chosen() fetches the raw flat-DT bootargs property and
passes it straight to bootcmdline_append(). That helper later feeds the
same pointer into strlcat(), which computes strlen(src) before copying.
Flat DT properties are external boot input, and this path does not
prove that bootargs is NUL-terminated within its declared bounds.

Reject unterminated bootargs properties before appending them to the
kernel command line.

Signed-off-by: Pengpeng Hou <pengpeng@xxxxxxxxxxx>
---
Changes since v1:
- use strnlen() instead of memchr() for the local NUL-termination check

arch/mips/kernel/setup.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index f9b228e33f3b..1ae6d0c0e1d6 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -31,6 +31,7 @@
 #include <linux/of_fdt.h>
 #include <linux/dmi.h>
 #include <linux/crash_dump.h>
+#include <linux/string.h>
 
 #include <asm/addrspace.h>
 #include <asm/bootinfo.h>
@@ -541,6 +542,9 @@ static int __init bootcmdline_scan_chosen(unsigned long node, const char *uname,
 
 	p = of_get_flat_dt_prop(node, "bootargs", &l);
 	if (p != NULL && l > 0) {
+		if (strnlen(p, l) >= l)
+			return 1;
+
 		bootcmdline_append(p, min(l, COMMAND_LINE_SIZE));
 		*dt_bootargs = true;
 	}
-- 
2.50.1 (Apple Git-155)