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Subject[patch 52/62] eCryptfs: use page_alloc not kmalloc to get a page of memory
2.6.26 -stable review patch.  If anyone has any objections, please let
us know.

------------------
From: Eric Sandeen <sandeen@redhat.com>

commit 7fcba054373d5dfc43d26e243a5c9b92069972ee upstream
Date: Mon, 28 Jul 2008 15:46:39 -0700
Subject: [patch 52/62] 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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/ecryptfs/crypto.c | 30 ++++++++++++++++++------------
1 file changed, 18 insertions(+), 12 deletions(-)

--- a/fs/ecryptfs/crypto.c
+++ b/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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