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kernel-2.6.18-238.el5.src.rpm

From: Eric Sandeen <sandeen@redhat.com>
Date: Tue, 29 Jul 2008 09:37:13 -0500
Subject: [fs] ecryptfs: use page_alloc to get a page of memory
Message-id: 488F2B19.8040004@redhat.com
O-Subject: [RHEL5.3 PATCH] ecryptfs: use page_alloc not kmalloc to get a page of memory
Bugzilla: 457058
RH-Acked-by: Jeff Layton <jlayton@redhat.com>
RH-Acked-by: Josef Bacik <jbacik@redhat.com>
RH-Acked-by: Larry Woodman <lwoodman@redhat.com>

For [Bug 457058] ecryptfs page-sized memory allocations can corrupt memory

Thanks,
-Eric

From: Eric Sandeen <sandeen@redhat.com>
Date: Mon, 28 Jul 2008 22:46:39 +0000 (-0700)
Subject: eCryptfs: use page_alloc not kmalloc to get a page of memory
X-Git-Tag: v2.6.27-rc1~8
X-Git-Url: http://git.engineering.redhat.com/?p=linux-2.6.git;a=commitdiff_plain;h=7fcba054373d5dfc43d26e243a5c9b92069972ee

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: Eric Sandeen <sandeen@redhat.com>
Acked-by: Michael Halcrow <mhalcrow@us.ibm.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: <stable@kernel.org>		[2.6.25.x, 2.6.26.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index 38859f0..e8b6fbf 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -422,8 +422,8 @@ 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;
 
@@ -439,14 +439,14 @@ 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++) {
@@ -474,7 +474,10 @@ 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;
 }
 
@@ -556,8 +559,8 @@ 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;
 
@@ -574,14 +577,14 @@ 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++) {
@@ -609,7 +612,10 @@ 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;
 }