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drivers/misc/lkdtm.c: fix race when crashpoint is hit multiple times before checking count

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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 <tdhimant@akamai.com>
Signed-off-by: Josh Hunt <johunt@akamai.com>
Acked-by: Ankita Garg <ankita@in.ibm.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Josh Hunt 2011-06-27 16:18:08 -07:00 committed by Linus Torvalds
parent 507c5f1224
commit aa2c96d6f3
1 changed files with 8 additions and 0 deletions
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8
drivers/misc/lkdtm.c
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@ -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 cname name)
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 which)
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)