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mm/kmemleak: fix possible wrong memory scanning period 

This commit contains 3 modifications:

1. Convert the type of jiffies_scan_wait to "unsigned long".

2. Use READ/WRITE_ONCE() for accessing "jiffies_scan_wait".

3. Fix the possible wrong memory scanning period.  If you set a large
   memory scanning period like blow, then the "secs" variable will be
   non-zero, however the value of "jiffies_scan_wait" will be zero.

    echo "scan=0x10000000" > /sys/kernel/debug/kmemleak

It is because the type of the msecs_to_jiffies()'s parameter is "unsigned
int", and the "secs * 1000" is larger than its max value.  This in turn
leads a unexpected jiffies_scan_wait, maybe zero.  We corret it by
replacing kstrtoul() with kstrtouint(), and check the msecs to prevent it
larger than UINT_MAX.

Link: https://lkml.kernel.org/r/20210613174022.23044-1-yanfei.xu@windriver.com
Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yanfei Xu 2021-06-28 19:35:01 -07:00 committed by Linus Torvalds
parent 65ebdeef10
commit 54dd200c5a
1 changed files with 12 additions and 6 deletions
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18
mm/kmemleak.c
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@ -219,7 +219,7 @@ static struct task_struct *scan_thread;
static unsigned long jiffies_min_age;
static unsigned long jiffies_last_scan;
/* delay between automatic memory scannings */
static signed long jiffies_scan_wait;
static unsigned long jiffies_scan_wait;
/* enables or disables the task stacks scanning */
static int kmemleak_stack_scan = 1;
/* protects the memory scanning, parameters and debug/kmemleak file access */
@ -1567,7 +1567,7 @@ static int kmemleak_scan_thread(void *arg)
}
while (!kthread_should_stop()) {
signed long timeout = jiffies_scan_wait;
signed long timeout = READ_ONCE(jiffies_scan_wait);
mutex_lock(&scan_mutex);
kmemleak_scan();
@ -1807,14 +1807,20 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
else if (strncmp(buf, "scan=off", 8) == 0)
stop_scan_thread();
else if (strncmp(buf, "scan=", 5) == 0) {
unsigned long secs;
unsigned secs;
unsigned long msecs;
ret = kstrtoul(buf + 5, 0, &secs);
ret = kstrtouint(buf + 5, 0, &secs);
if (ret < 0)
goto out;
msecs = secs * MSEC_PER_SEC;
if (msecs > UINT_MAX)
msecs = UINT_MAX;
stop_scan_thread();
if (secs) {
jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
if (msecs) {
WRITE_ONCE(jiffies_scan_wait, msecs_to_jiffies(msecs));
start_scan_thread();
}
} else if (strncmp(buf, "scan", 4) == 0)