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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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