Re: [kernel-hardening] Re: [patch 2/2] fs, proc: Introduce the/proc/<pid>/map_files/ directory v6

[Vasiliy Kulikov]

Hi Cyrill,

On Thu, Sep 08, 2011 at 10:04 +0400, Cyrill Gorcunov wrote:
> +static int map_files_d_revalidate(struct dentry *dentry, struct nameidata *nd)
> +{
> +	unsigned long vm_start, vm_end;
> +	bool exact_vma_exists = false;
> +	struct task_struct *task;
> +	const struct cred *cred;
> +	struct mm_struct *mm;
> +	struct inode *inode;
> +
> +	if (nd && nd->flags & LOOKUP_RCU)
> +		return -ECHILD;
> +
> +	inode = dentry->d_inode;
> +	task = get_proc_task(inode);
> +	if (!task)
> +		goto out;
> +
> +	if (!ptrace_may_access(task, PTRACE_MODE_READ))

        put_task_struct(task) belongs here.

> +		goto out;
> +
> +	mm = get_task_mm(task);
> +	put_task_struct(task);
> +	if (!mm)
> +		goto out;
> +
> +	if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) {
> +		down_read(&mm->mmap_sem);
> +		exact_vma_exists = !!find_exact_vma(mm, vm_start, vm_end);
> +		up_read(&mm->mmap_sem);
> +	}
> +
> +	mmput(mm);
> +
> +	if (exact_vma_exists) {
> +		if (task_dumpable(task)) {
> +			rcu_read_lock();
> +			cred = __task_cred(task);
> +			inode->i_uid = cred->euid;
> +			inode->i_gid = cred->egid;
> +			rcu_read_unlock();
> +		} else {
> +			inode->i_uid = 0;
> +			inode->i_gid = 0;
> +		}
> +		security_task_to_inode(task, inode);
> +		return 1;
> +	}
> +out:
> +	d_drop(dentry);
> +	return 0;
> +}

Thanks,

-- 
Vasiliy Kulikov
http://www.openwall.com - bringing security into open computing environments
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