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SubjectRe: [PATCH 1/3] extend get/setrlimit to support setting rlimits external to a process (v3)
Neil Horman wrote:
> Augment /proc/<pid>/limits file to support limit setting
>(...)
> /* Display limits for a process */
> -static int proc_pid_limits(struct task_struct *task, char *buffer)
> +static ssize_t proc_pid_limit_read(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> {
> unsigned int i;
> - int count = 0;
> unsigned long flags;
> - char *bufptr = buffer;
> + char *bufptr;
> + size_t bcount = 0;
> + size_t ccount = 0;
> + struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
>
> struct rlimit rlim[RLIM_NLIMITS];
>
> + bufptr = kzalloc(PAGE_SIZE, GFP_KERNEL);
> + if (!bufptr)
> + goto out;
> +
> if (!lock_task_sighand(task, &flags))
> - return 0;
> + goto out;

memory leak (bufptr)

> memcpy(rlim, task->signal->rlim, sizeof(struct rlimit) * RLIM_NLIMITS);
> unlock_task_sighand(task, &flags);
>
> /*
> * print the file header
> */
> - count += sprintf(&bufptr[count], "%-25s %-20s %-20s %-10s\n",
> + bcount += sprintf(&bufptr[bcount], "%-25s %-20s %-20s %-10s\n",
> "Limit", "Soft Limit", "Hard Limit", "Units");
>
> for (i = 0; i < RLIM_NLIMITS; i++) {
> if (rlim[i].rlim_cur == RLIM_INFINITY)
> - count += sprintf(&bufptr[count], "%-25s %-20s ",
> + bcount += sprintf(&bufptr[bcount], "%-25s %-20s ",
> lnames[i].name, "unlimited");
> else
> - count += sprintf(&bufptr[count], "%-25s %-20lu ",
> + bcount += sprintf(&bufptr[bcount], "%-25s %-20lu ",
> lnames[i].name, rlim[i].rlim_cur);
>
> if (rlim[i].rlim_max == RLIM_INFINITY)
> - count += sprintf(&bufptr[count], "%-20s ", "unlimited");
> + bcount += sprintf(&bufptr[bcount], "%-20s ",
> + "unlimited");
> else
> - count += sprintf(&bufptr[count], "%-20lu ",
> + bcount += sprintf(&bufptr[bcount], "%-20lu ",
> rlim[i].rlim_max);
>
> if (lnames[i].unit)
> - count += sprintf(&bufptr[count], "%-10s\n",
> + bcount += sprintf(&bufptr[bcount], "%-10s\n",
> lnames[i].unit);
> else
> - count += sprintf(&bufptr[count], "\n");
> + bcount += sprintf(&bufptr[bcount], "\n");
> + }
> +
> + if (*ppos >= bcount)
> + goto out_task;

again

> +
> + ccount = min(count, (size_t)(bcount-(*ppos)));
> + ccount = ccount - copy_to_user(buf, &bufptr[*ppos], ccount);
> + *ppos += ccount;
> + kfree(bufptr);
> +out_task:
> + put_task_struct(task);
> +out:
> + return ccount;
> +}
> +
> +static ssize_t proc_pid_limit_write(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + char *buffer;
> + char *element, *vmc, *vmm;
> + struct rlimit new_rlim;
> + unsigned long flags;
> + int i;
> + int index = -1;
> + size_t wcount = 0;
> + struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
> +
> +
> + if (*ppos != 0)
> + goto out;
> +
> + if (count > 128)
> + goto out;
> + buffer = kzalloc(128, GFP_KERNEL);
> +
> + if (!buffer)
> + goto out;

element, vmc, vmm are not initialized and you kfree them in this case

> +
> + element = kzalloc(sizeof(buffer), GFP_KERNEL);
> + vmc = kzalloc(sizeof(buffer), GFP_KERNEL);
> + vmm = kzalloc(sizeof(buffer), GFP_KERNEL);

sizeof(buffer) == 4 or 8 - pretty short buffer...

> +
> + if (!element || !vmm || !vmc)
> + goto out_free;
> +
> + wcount = count - copy_from_user(buffer, buf, count);
> + if (wcount < count)
> + goto out_free;

copy_from_user usage usually looks like:
if (copy_from_user()) {
ret = -EFAULT;
goto err;
}
you don't seem to use copy_from_user return value for anything useful
> +
> + i = sscanf(buffer, "%s %s %s", element, vmc, vmm);

what if user pass strings longer than size of buffers?

> +
> + if (i < 3)
> + goto out_free;
> +
> + for (i = 0; i <= strlen(element); i++)
> + element[i] = tolower(element[i]);

it's harmless, but should be "i < strlen"

> +
> + if (!strncmp(vmc, "unlimited", 9))
> + new_rlim.rlim_cur = RLIM_INFINITY;
> + else
> + new_rlim.rlim_cur = simple_strtoull(vmc, NULL, 10);
> +
> + if (!strncmp(vmm, "unlimited", 9))
> + new_rlim.rlim_max = RLIM_INFINITY;
> + else
> + new_rlim.rlim_max = simple_strtoull(vmm, NULL, 10);
> +
> + for (i = 0; i < RLIM_NLIMITS; i++) {
> + if ((lnames[i].match) &&
> + !strncmp(element, lnames[i].match,
> + strlen(lnames[i].match))) {
> + index = i;
> + break;
> + }
> }
>
> + if (!lock_task_sighand(task, &flags))
> + goto out_free;
> +
> + if ((index >= 0) && (index < RLIM_NLIMITS))
> + do_setrlimit(index, &new_rlim, task);
> +
> + unlock_task_sighand(task, &flags);
> +
> +out_free:
> + kfree(element);
> + kfree(vmc);
> + kfree(vmm);
> + kfree(buffer);
> +out:
> + *ppos += count;
> + put_task_struct(task);
> return count;
> }
>
> (...)


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