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SubjectRe: [PATCH] eCryptfs - use page_alloc not kmalloc to get a page of memory
On Mon, Jul 28, 2008 at 11:13:03AM -0500, Eric Sandeen wrote:
> With SLUB debugging turned on in 2.6.26, I was getting memory corruption
> when testing eCryptfs. The root cause turned out to be that eCryptfs
> was doing kmalloc(PAGE_CACHE_SIZE); virt_to_page() and treating that
> as a nice page-aligned chunk of memory. But at least with SLUB debugging
> on, this is not always true, and the page we get from virt_to_page does
> not necessarily match the PAGE_CACHE_SIZE worth of memory we got from
> kmalloc.
>
> My simple testcase was 2 loops doing "rm -f fileX; cp /tmp/fileX ." for
> 2 different multi-megabyte files. With this change I no longer see
> the corruption.
>
> Thanks,
> -Eric
>
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Acked-by: Michael Halcrow <mhalcrow@us.ibm.com>

> ---
>
> Index: linux-2.6.26/fs/ecryptfs/crypto.c
> ===================================================================
> --- linux-2.6.26.orig/fs/ecryptfs/crypto.c
> +++ linux-2.6.26/fs/ecryptfs/crypto.c
> @@ -474,8 +474,8 @@ int ecryptfs_encrypt_page(struct page *p
> {
> struct inode *ecryptfs_inode;
> struct ecryptfs_crypt_stat *crypt_stat;
> - char *enc_extent_virt = NULL;
> - struct page *enc_extent_page;
> + char *enc_extent_virt;
> + struct page *enc_extent_page = NULL;
> loff_t extent_offset;
> int rc = 0;
>
> @@ -491,14 +491,14 @@ int ecryptfs_encrypt_page(struct page *p
> page->index);
> goto out;
> }
> - enc_extent_virt = kmalloc(PAGE_CACHE_SIZE, GFP_USER);
> - if (!enc_extent_virt) {
> + enc_extent_page = alloc_page(GFP_USER);
> + if (!enc_extent_page) {
> rc = -ENOMEM;
> ecryptfs_printk(KERN_ERR, "Error allocating memory for "
> "encrypted extent\n");
> goto out;
> }
> - enc_extent_page = virt_to_page(enc_extent_virt);
> + enc_extent_virt = kmap(enc_extent_page);
> for (extent_offset = 0;
> extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
> extent_offset++) {
> @@ -526,7 +526,10 @@ int ecryptfs_encrypt_page(struct page *p
> }
> }
> out:
> - kfree(enc_extent_virt);
> + if (enc_extent_page) {
> + kunmap(enc_extent_page);
> + __free_page(enc_extent_page);
> + }
> return rc;
> }
>
> @@ -608,8 +611,8 @@ int ecryptfs_decrypt_page(struct page *p
> {
> struct inode *ecryptfs_inode;
> struct ecryptfs_crypt_stat *crypt_stat;
> - char *enc_extent_virt = NULL;
> - struct page *enc_extent_page;
> + char *enc_extent_virt;
> + struct page *enc_extent_page = NULL;
> unsigned long extent_offset;
> int rc = 0;
>
> @@ -626,14 +629,14 @@ int ecryptfs_decrypt_page(struct page *p
> page->index);
> goto out;
> }
> - enc_extent_virt = kmalloc(PAGE_CACHE_SIZE, GFP_USER);
> - if (!enc_extent_virt) {
> + enc_extent_page = alloc_page(GFP_USER);
> + if (!enc_extent_page) {
> rc = -ENOMEM;
> ecryptfs_printk(KERN_ERR, "Error allocating memory for "
> "encrypted extent\n");
> goto out;
> }
> - enc_extent_page = virt_to_page(enc_extent_virt);
> + enc_extent_virt = kmap(enc_extent_page);
> for (extent_offset = 0;
> extent_offset < (PAGE_CACHE_SIZE / crypt_stat->extent_size);
> extent_offset++) {
> @@ -661,7 +664,10 @@ int ecryptfs_decrypt_page(struct page *p
> }
> }
> out:
> - kfree(enc_extent_virt);
> + if (enc_extent_page) {
> + kunmap(enc_extent_page);
> + __free_page(enc_extent_page);
> + }
> return rc;
> }
>
>


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