Commit 7fcba054 authored by Eric Sandeen's avatar Eric Sandeen Committed by Linus Torvalds
Browse files

eCryptfs: use page_alloc not kmalloc to get a page of memory 



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.

Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Acked-by: default avatarMichael Halcrow <mhalcrow@us.ibm.com>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Cc: <stable@kernel.org>		[2.6.25.x, 2.6.26.x]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 25947d5a

fs/ecryptfs/crypto.c

+18 −12
Original line number Diff line number Diff line
@@ -475,8 +475,8 @@ int ecryptfs_encrypt_page(struct page *page) 
{

	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;
@@ -492,14 +492,14 @@ int ecryptfs_encrypt_page(struct page *page) 
			       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++) {
@@ -527,7 +527,10 @@ int ecryptfs_encrypt_page(struct page *page) 
		}

	}

out:

	kfree(enc_extent_virt);

	if (enc_extent_page) {

		kunmap(enc_extent_page);

		__free_page(enc_extent_page);

	}

	return rc;

}
@@ -609,8 +612,8 @@ int ecryptfs_decrypt_page(struct page *page) 
{

	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;
@@ -627,14 +630,14 @@ int ecryptfs_decrypt_page(struct page *page) 
			       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++) {
@@ -662,7 +665,10 @@ int ecryptfs_decrypt_page(struct page *page) 
		}

	}

out:

	kfree(enc_extent_virt);

	if (enc_extent_page) {

		kunmap(enc_extent_page);

		__free_page(enc_extent_page);

	}

	return rc;

}

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