[PATCH] init/main.c: Fix potential static_command_line memory overflow

[Yuntao Wang <ytcoode@gmail.com>]

We allocate memory of size 'xlen + strlen(boot_command_line) + 1' for
static_command_line, but the strings copied into static_command_line are
extra_command_line and command_line, rather than extra_command_line and
boot_command_line.

When strlen(command_line) > strlen(boot_command_line), static_command_line
will overflow.

Fixes: f5c7310ac73e ("init/main: add checks for the return value of memblock_alloc*()")
Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
 init/main.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/init/main.c b/init/main.c
index 2ca52474d0c3..a7b1f5f3e3b6 100644
--- a/init/main.c
+++ b/init/main.c
@@ -625,11 +625,13 @@ static void __init setup_command_line(char *command_line)
 	if (extra_init_args)
 		ilen = strlen(extra_init_args) + 4; /* for " -- " */
 
-	len = xlen + strlen(boot_command_line) + 1;
+	len = xlen + strlen(boot_command_line) + ilen + 1;
 
-	saved_command_line = memblock_alloc(len + ilen, SMP_CACHE_BYTES);
+	saved_command_line = memblock_alloc(len, SMP_CACHE_BYTES);
 	if (!saved_command_line)
-		panic("%s: Failed to allocate %zu bytes\n", __func__, len + ilen);
+		panic("%s: Failed to allocate %zu bytes\n", __func__, len);
+
+	len = xlen + strlen(command_line) + 1;
 
 	static_command_line = memblock_alloc(len, SMP_CACHE_BYTES);
 	if (!static_command_line)
-- 
2.44.0