From: Josh Hunt <[email protected]> We observed the crash point count going negative in cases where the crash point is hit multiple times before the check of "count == 0" is done. Because of this we never call lkdtm_do_action(). This patch just adds a spinlock to protect count.
Reported-by: Tapan Dhimant <[email protected]> Signed-off-by: Josh Hunt <[email protected]> Acked-by: Ankita Garg <[email protected]> Cc: <[email protected]> Signed-off-by: Andrew Morton <[email protected]> --- drivers/misc/lkdtm.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff -puN drivers/misc/lkdtm.c~drivers-misc-lkdtmc-fix-race-when-crashpoint-is-hit-multiple-times-before-checking-count drivers/misc/lkdtm.c --- a/drivers/misc/lkdtm.c~drivers-misc-lkdtmc-fix-race-when-crashpoint-is-hit-multiple-times-before-checking-count +++ a/drivers/misc/lkdtm.c @@ -120,6 +120,7 @@ static int recur_count = REC_NUM_DEFAULT static enum cname cpoint = CN_INVALID; static enum ctype cptype = CT_NONE; static int count = DEFAULT_COUNT; +static DEFINE_SPINLOCK(count_lock); module_param(recur_count, int, 0644); MODULE_PARM_DESC(recur_count, " Recursion level for the stack overflow test, "\ @@ -230,11 +231,14 @@ static const char *cp_name_to_str(enum c static int lkdtm_parse_commandline(void) { int i; + unsigned long flags; if (cpoint_count < 1 || recur_count < 1) return -EINVAL; + spin_lock_irqsave(&count_lock, flags); count = cpoint_count; + spin_unlock_irqrestore(&count_lock, flags); /* No special parameters */ if (!cpoint_type && !cpoint_name) @@ -349,6 +353,9 @@ static void lkdtm_do_action(enum ctype w static void lkdtm_handler(void) { + unsigned long flags; + + spin_lock_irqsave(&count_lock, flags); count--; printk(KERN_INFO "lkdtm: Crash point %s of type %s hit, trigger in %d rounds\n", cp_name_to_str(cpoint), cp_type_to_str(cptype), count); @@ -357,6 +364,7 @@ static void lkdtm_handler(void) lkdtm_do_action(cptype); count = cpoint_count; } + spin_unlock_irqrestore(&count_lock, flags); } static int lkdtm_register_cpoint(enum cname which) _ _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
