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Commit 5020ded7 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Greg Kroah-Hartman
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tty: nozomi: avoid sprintf buffer overflow 

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.

A lot of the code here is unnecessary and can be expressed in a simpler
way, relying on the fact that removing the 'DEBUG' macro will also get
rid of all pr_debug() calls. This change should not change any of the
output but avoids both the stack overflow and the gcc crash.

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

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f209fa03

drivers/tty/nozomi.c

+12 −35
Original line number Diff line number Diff line
@@ -63,44 +63,23 @@ 


#define VERSION_STRING DRIVER_DESC " 2.1d"



/*    Macros definitions */



/* Default debug printout level */

#define NOZOMI_DEBUG_LEVEL 0x00

static int debug = NOZOMI_DEBUG_LEVEL;

module_param(debug, int, S_IRUGO | S_IWUSR);



#define P_BUF_SIZE 128

#define NFO(_err_flag_, args...)				\

/*    Macros definitions */

#define DBG_(lvl, fmt, args...)				\

do {							\

	char tmp[P_BUF_SIZE];					\

	snprintf(tmp, sizeof(tmp), ##args);			\

	printk(_err_flag_ "[%d] %s(): %s\n", __LINE__,		\

		__func__, tmp);				\

	if (lvl & debug)				\

		pr_debug("[%d] %s(): " fmt "\n",	\

			 __LINE__, __func__,  ##args);	\

} while (0)



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

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

#define DBG3(args...) D_(0x04, ##args)

#define DBG4(args...) D_(0x08, ##args)

#define DBG5(args...) D_(0x10, ##args)

#define DBG6(args...) D_(0x20, ##args)

#define DBG7(args...) D_(0x40, ##args)

#define DBG8(args...) D_(0x80, ##args)



#ifdef DEBUG

/* Do we need this settable at runtime? */

static int debug = NOZOMI_DEBUG_LEVEL;



#define D(lvl, args...)  do \

			{if (lvl & debug) NFO(KERN_DEBUG, ##args); } \

			while (0)

#define D_(lvl, args...) D(lvl, ##args)



/* These printouts are always printed */



#else

static int debug;

#define D_(lvl, args...)

#endif

#define DBG1(args...) DBG_(0x01, ##args)

#define DBG2(args...) DBG_(0x02, ##args)

#define DBG3(args...) DBG_(0x04, ##args)

#define DBG4(args...) DBG_(0x08, ##args)



/* TODO: rewrite to optimize macros... */
@@ -1943,7 +1922,5 @@ static __exit void nozomi_exit(void) 
module_init(nozomi_init);

module_exit(nozomi_exit);



module_param(debug, int, S_IRUGO | S_IWUSR);



MODULE_LICENSE("Dual BSD/GPL");

MODULE_DESCRIPTION(DRIVER_DESC);