efi/printf: Handle null string input

Print "(null)" for 's' if the input is a NULL pointer.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200518190716.751506-14-nivedita@alum.mit.edu
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

diff --git a/drivers/firmware/efi/libstub/vsprintf.c b/drivers/firmware/efi/libstub/vsprintf.c
index 27685c726c6400b47d34ad7843def9959ca7ebb8..d427a7b1ef64b23e92fb104c71888fa1e54c62d6 100644 (file)
--- a/drivers/firmware/efi/libstub/vsprintf.c
+++ b/drivers/firmware/efi/libstub/vsprintf.c
@@ -14,6 +14,7 @@
 
 #include <linux/compiler.h>
 #include <linux/ctype.h>
+#include <linux/limits.h>
 #include <linux/string.h>
 
 static int skip_atoi(const char **s)
@@ -356,7 +357,11 @@ int vsprintf(char *buf, const char *fmt, va_list ap)
                        continue;
 
                case 's':
+                       if (precision < 0)
+                               precision = INT_MAX;
                        s = va_arg(args, char *);
+                       if (!s)
+                               s = precision < 6 ? "" : "(null)";
                        len = strnlen(s, precision);
 
                        if (!(flags & LEFT))