Messages in this thread | | | Date | Thu, 1 Sep 2022 15:31:51 +0700 | Subject | Re: [PATCH 3/3] mm,page_owner: Filter out stacks by a threshold counter | From | Ammar Faizi <> |
| |
On 9/1/22 11:42 AM, Oscar Salvador wrote:> +static ssize_t read_page_owner_threshold(struct file *file, char __user *buf, > + size_t count, loff_t *pos) > +{ > + char *kbuf; > + int ret = 0; > + > + count = min_t(size_t, count, PAGE_SIZE); > + > + if (*pos >= count) > + return 0; > + > + kbuf = kmalloc(count, GFP_KERNEL); > + if (!kbuf) > + return ENOMEM;
Missing a negative sign, return -ENOMEM.
> + ret = scnprintf(kbuf, count, "%lu\n", threshold_count); > + if (copy_to_user(buf, kbuf, ret)) > + ret = -EFAULT; > + > + *pos += count; > + kfree(kbuf); > + > + return ret; > +} > + > +static ssize_t write_page_owner_threshold(struct file *file, const char __user *buf, > + size_t count, loff_t *pos) > +{ > + char *kbuf; > + int ret = 0; > + > + count = min_t(size_t, count, PAGE_SIZE); > + kbuf = kmalloc(count, GFP_KERNEL);
This looks overestimating to me. For unsigned long, on a 64-bit system has max val 18446744073709551615 (20 chars).
You can use stack a allocated local variable with length 21. No need to use kmalloc(). The same way with the read() op.
> + if (!kbuf) > + return -ENOMEM; > + > + if (copy_from_user(kbuf, buf, count)) { > + ret = -EFAULT; > + goto out; > + } > + > + kbuf[count - 1] = '\0'; > + > + ret = kstrtoul(kbuf, 10, &threshold_count); > + > +out: > + kfree(kbuf); > + return ret ? ret : count; > +} > + > +static const struct file_operations proc_page_owner_threshold = { > + .read = read_page_owner_threshold, > + .write = write_page_owner_threshold, > +};
-- Ammar Faizi
| |