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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: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hifive-unleashed-5.1
Arnd Bergmann 2016-11-29 12:51:04 +01:00 committed by Greg Kroah-Hartman
parent f209fa03fc
commit 5020ded783
1 changed files with 12 additions and 35 deletions
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47
drivers/tty/nozomi.c
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@ -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...) \
do { \
char tmp[P_BUF_SIZE]; \
snprintf(tmp, sizeof(tmp), ##args); \
printk(_err_flag_ "[%d] %s(): %s\n", __LINE__, \
__func__, tmp); \
/* Macros definitions */
#define DBG_(lvl, fmt, args...) \
do { \
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);