Messages in this thread | | | Date | Mon, 28 Jul 2008 11:25:03 -0500 | From | Michael Halcrow <> | Subject | Re: [PATCH] eCryptfs - use page_alloc not kmalloc to get a page of memory |
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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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