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Date: Mon, 28 Jul 2008 11:13:03 -0500
From: Eric Sandeen <sandeen@...hat.com>
To: linux-kernel Mailing List <linux-kernel@...r.kernel.org>
CC: Michael Halcrow <mhalcrow@...ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH] 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.
Thanks,
-Eric
Signed-off-by: Eric Sandeen <sandeen@...hat.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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