[PATCH] powerpc/kexec_file: use snprintf to simplify setup_kdump_cmdline

[PATCH] powerpc/kexec_file: use snprintf to simplify setup_kdump_cmdline

[Thorsten Blum]

Replace the manual string length accounting, memcpy(), and NUL
termination with a single snprintf() call to prepend the elfcorehdr=
address and to detect string truncation at the same time.

Use kmalloc() to avoid unnecessarily zeroing the memory. While at it,
also use "prepending" instead of "appending" in the error message.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 arch/powerpc/kexec/file_load.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kexec/file_load.c b/arch/powerpc/kexec/file_load.c
index 4284f76cbef5..597998235136 100644
--- a/arch/powerpc/kexec/file_load.c
+++ b/arch/powerpc/kexec/file_load.c
@@ -36,25 +36,19 @@
 char *setup_kdump_cmdline(struct kimage *image, char *cmdline,
 			  unsigned long cmdline_len)
 {
-	int elfcorehdr_strlen;
 	char *cmdline_ptr;
 
-	cmdline_ptr = kzalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
+	cmdline_ptr = kmalloc(COMMAND_LINE_SIZE, GFP_KERNEL);
 	if (!cmdline_ptr)
 		return NULL;
 
-	elfcorehdr_strlen = sprintf(cmdline_ptr, "elfcorehdr=0x%lx ",
-				    image->elf_load_addr);
-
-	if (elfcorehdr_strlen + cmdline_len > COMMAND_LINE_SIZE) {
-		pr_err("Appending elfcorehdr=<addr> exceeds cmdline size\n");
+	if (snprintf(cmdline_ptr, COMMAND_LINE_SIZE, "elfcorehdr=0x%lx %s",
+		     image->elf_load_addr, cmdline_len ? cmdline : "") >= COMMAND_LINE_SIZE) {
+		pr_err("Prepending elfcorehdr=<addr> exceeds cmdline size\n");
 		kfree(cmdline_ptr);
 		return NULL;
 	}
 
-	memcpy(cmdline_ptr + elfcorehdr_strlen, cmdline, cmdline_len);
-	// Ensure it's nul terminated
-	cmdline_ptr[COMMAND_LINE_SIZE - 1] = '\0';
 	return cmdline_ptr;
 }