include, lib: add __printf attributes to several function prototypes

Using __printf attributes helps to detect several format string issues
at compile time (even though -Wformat-security is currently disabled in
Makefile).  For example it can detect when formatting a pointer as a
number, like the issue fixed in commit a3fa71c40f18 ("wl18xx: show
rx_frames_per_rates as an array as it really is"), or when the arguments
do not match the format string, c.f.  for example commit 5ce1aca81435
("reiserfs: fix __RASSERT format string").

To prevent similar bugs in the future, add a __printf attribute to every
function prototype which needs one in include/linux/ and lib/.  These
functions were mostly found by using gcc's -Wsuggest-attribute=format
flag.

Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 4 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 5f0be58640ea..5582410727cb 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -411,7 +411,8 @@ extern __printf(3, 0)
 int vscnprintf(char *buf, size_t size, const char *fmt, va_list args);
 extern __printf(2, 3)
 char *kasprintf(gfp_t gfp, const char *fmt, ...);
-extern char *kvasprintf(gfp_t gfp, const char *fmt, va_list args);
+extern __printf(2, 0)
+char *kvasprintf(gfp_t gfp, const char *fmt, va_list args);
 
 extern __scanf(2, 3)
 int sscanf(const char *, const char *, ...);
@@ -679,10 +680,10 @@ do {									\
                 __ftrace_vprintk(_THIS_IP_, fmt, vargs);                \
 } while (0)
 
-extern int
+extern __printf(2, 0) int
 __ftrace_vbprintk(unsigned long ip, const char *fmt, va_list ap);
 
-extern int
+extern __printf(2, 0) int
 __ftrace_vprintk(unsigned long ip, const char *fmt, va_list ap);
 
 extern void ftrace_dump(enum ftrace_dump_mode oops_dump_mode);
@@ -702,7 +703,7 @@ int trace_printk(const char *fmt, ...)
 {
         return 0;
 }
-static inline int
+static __printf(1, 0) inline int
 ftrace_vprintk(const char *fmt, va_list ap)
 {
         return 0;