On Tue, Jan 09, 2007 at 02:42:03PM -0800, Andrew Morton wrote:
> On Tue, 9 Jan 2007 16:23:37 -0600
> Michael Halcrow <[email protected]> wrote:
>
> > + page_virt = (char *)kmap(page);
>
> Do we _have_ to use kmap here? It's slow and theoretically deadlocky.
> kmap_atomic() is much preferred.
>
> Can the other kmap() calls in ecryptfs be converted?
We will look into doing this.
> We'd actually like to remove kmap() one day. Not much chance of that, but
> it's an objective.
>
> > + if (!page_virt) {
> > + rc = -ENOMEM;
> > + printk(KERN_ERR "Error mapping page\n");
> > + goto out;
> > + }
> > + memset(page_virt, 0, PAGE_CACHE_SIZE);
> > + if (page->index == 0) {
> > + rc = ecryptfs_read_xattr_region(
> > + page_virt, file->f_path.dentry);
>
> Are we assured that ecryptfs_read_xattr_region() cannot overrun the
> page?
Yes:
---
int ecryptfs_read_xattr_region(char *page_virt, struct dentry*ecryptfs_dentry)
{
ssize_t size;
int rc = 0;
size = ecryptfs_getxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME,
page_virt, ECRYPTFS_DEFAULT_EXTENT_SIZE);
---
That winds up calling the lower filesystem's getxattr with
ECRYPTFS_DEFAULT_EXTENT_SIZE as the size parameter. eCryptfs validates
this value against PAGE_CACHE_SIZE in main.c::ecryptfs_init().
> > + set_header_info(page_virt, crypt_stat);
> > + }
>
> The kernel must always run flush_dcache_page() after modifying a pagecache
> page by hand. Please review all of ecryptfs for this.
We will work on some patches to address these issues.
Mike
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