[PATCH] tty: nozomi: avoid sprintf buffer overflow

From: Arnd Bergmann
Date: Mon Nov 28 2016 - 16:04:58 EST

Testing with a gcc-7 snapshot produced an internal compiler error
for this file:

drivers/tty/nozomi.c: In function 'receive_flow_control':
drivers/tty/nozomi.c:919:12: internal compiler error: in get_substring_ranges_for_loc, at input.c:1388
static int receive_flow_control(struct nozomi *dc)

I've reported this at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78569
but also noticed that the code line contains a stack overflow, as it prints
a string into a slightly shorter fixed-length 'tmp' variable.

I don't see any point in the temporary variable, we can simply use
pr_debug() to print the output directly. This change should not change
any of the output but avoids both the stack overflow and the gcc

The stack overflow will not happen unless a module load parameter is
also set to enable the debug messages.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
drivers/tty/nozomi.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/tty/nozomi.c b/drivers/tty/nozomi.c
index e2020a691058..17a182b28d52 100644
--- a/drivers/tty/nozomi.c
+++ b/drivers/tty/nozomi.c
@@ -69,13 +69,8 @@

#define P_BUF_SIZE 128
-#define NFO(_err_flag_, args...) \
-do { \
- char tmp[P_BUF_SIZE]; \
- snprintf(tmp, sizeof(tmp), ##args); \
- printk(_err_flag_ "[%d] %s(): %s\n", __LINE__, \
- __func__, tmp); \
-} while (0)
+#define NFO(_err_flag_, fmt, args...) \
+ pr_debug("[%d] %s(): " fmt "\n", __LINE__, __func__, ##args);

#define DBG1(args...) D_(0x01, ##args)
#define DBG2(args...) D_(0x02, ##args)