[PATCH] powerpc/boot: avoid overflowing the bootwrapper printf buffer with bootargs

[Pengpeng Hou <pengpeng@iscas.ac.cn>]

The bootwrapper printf path formats strings through a fixed 1024-byte
scratch buffer in arch/powerpc/boot/stdio.c.

Both prep_cmdline() in main.c and ps3.c print the full bootargs string
with a %s conversion even though the command line buffer itself is 2048
bytes. A long firmware-provided or built-in command line can therefore
overrun the bootwrapper printf staging buffer while the kernel is still
starting.

Print the command line through console_ops.write() in bounded chunks
instead of passing it to printf() as a single %s argument.

Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
---
 arch/powerpc/boot/main.c | 12 +++++++++++-
 arch/powerpc/boot/ps3.c  | 12 +++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/boot/main.c b/arch/powerpc/boot/main.c
index 2c0e2a1cab01..d02f77ad4df7 100644
--- a/arch/powerpc/boot/main.c
+++ b/arch/powerpc/boot/main.c
@@ -193,6 +193,16 @@ static inline void prep_esm_blob(struct addr_range vmlinux, void *chosen) { }
 static char cmdline[BOOT_COMMAND_LINE_SIZE]
 	__attribute__((__section__("__builtin_cmdline")));
 
+static void print_cmdline(const char *prefix, const char *suffix)
+{
+	size_t len = strnlen(cmdline, BOOT_COMMAND_LINE_SIZE - 1);
+
+	printf("%s", prefix);
+	if (console_ops.write && len)
+		console_ops.write(cmdline, len);
+	printf("%s", suffix);
+}
+
 static void prep_cmdline(void *chosen)
 {
 	unsigned int getline_timeout = 5000;
@@ -207,7 +217,7 @@ static void prep_cmdline(void *chosen)
 	if (cmdline[0] == '\0')
 		getprop(chosen, "bootargs", cmdline, BOOT_COMMAND_LINE_SIZE-1);
 
-	printf("\n\rLinux/PowerPC load: %s", cmdline);
+	print_cmdline("\n\rLinux/PowerPC load: ", "");
 
 	/* If possible, edit the command line */
 	if (console_ops.edit_cmdline && getline_timeout)
diff --git a/arch/powerpc/boot/ps3.c b/arch/powerpc/boot/ps3.c
index 89ff46b8b225..2f17b99c713c 100644
--- a/arch/powerpc/boot/ps3.c
+++ b/arch/powerpc/boot/ps3.c
@@ -31,6 +31,16 @@ BSS_STACK(4096);
 static char cmdline[BOOT_COMMAND_LINE_SIZE]
 	__attribute__((__section__("__builtin_cmdline")));
 
+static void print_cmdline(const char *prefix, const char *suffix)
+{
+	size_t len = strnlen(cmdline, BOOT_COMMAND_LINE_SIZE - 1);
+
+	printf("%s", prefix);
+	if (console_ops.write && len)
+		console_ops.write(cmdline, len);
+	printf("%s", suffix);
+}
+
 static void prep_cmdline(void *chosen)
 {
 	if (cmdline[0] == '\0')
@@ -38,7 +48,7 @@ static void prep_cmdline(void *chosen)
 	else
 		setprop_str(chosen, "bootargs", cmdline);
 
-	printf("cmdline: '%s'\n", cmdline);
+	print_cmdline("cmdline: '", "'\n");
 }
 
 static void ps3_console_write(const char *buf, int len)
-- 
2.50.1 (Apple Git-155)