nobh_prepare_write leaks data similarly to how simple_prepare_write did. Fix
by not marking the page uptodate until nobh_commit_write time. Again, this
could break weird use-cases, but none appear to exist in the tree.
We can safely remove the set_page_dirty, because as the comment says,
nobh_commit_write does set_page_dirty. If a filesystem wants to allocate
backing store for a page dirtied via mmap, page_mkwrite is the suggested
approach.
Signed-off-by: Nick Piggin <[EMAIL PROTECTED]>
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -2245,7 +2245,6 @@ int nobh_prepare_write(struct page *page
int i;
int ret = 0;
int is_mapped_to_disk = 1;
- int dirtied_it = 0;
if (PageMappedToDisk(page))
return 0;
@@ -2282,14 +2281,10 @@ int nobh_prepare_write(struct page *page
continue;
if (buffer_new(&map_bh) || !buffer_mapped(&map_bh)) {
kaddr = kmap_atomic(page, KM_USER0);
- if (block_start < from) {
+ if (block_start < from)
memset(kaddr+block_start, 0, from-block_start);
- dirtied_it = 1;
- }
- if (block_end > to) {
+ if (block_end > to)
memset(kaddr + to, 0, block_end - to);
- dirtied_it = 1;
- }
flush_dcache_page(page);
kunmap_atomic(kaddr, KM_USER0);
continue;
@@ -2344,17 +2339,6 @@ int nobh_prepare_write(struct page *page
if (is_mapped_to_disk)
SetPageMappedToDisk(page);
- SetPageUptodate(page);
-
- /*
- * Setting the page dirty here isn't necessary for the prepare_write
- * function - commit_write will do that. But if/when this function is
- * used within the pagefault handler to ensure that all mmapped pages
- * have backing space in the filesystem, we will need to dirty the page
- * if its contents were altered.
- */
- if (dirtied_it)
- set_page_dirty(page);
return 0;
@@ -2384,6 +2368,7 @@ int nobh_commit_write(struct file *file,
struct inode *inode = page->mapping->host;
loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
+ SetPageUptodate(page);
set_page_dirty(page);
if (pos > inode->i_size) {
i_size_write(inode, pos);
-
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