Andrew Morton wrote:
On Tue, 13 Feb 2007 20:07:44 -0600 "Eric Van Hensbergen" <[email protected]> wrote:
On 2/13/07, Andrew Morton <[email protected]> wrote:
On Tue, 13 Feb 2007 17:55:31 -0600 Eric Van Hensbergen <[email protected]> wrote:
+int v9fs_prepare_write(struct file *file, struct page *page,
+ unsigned from, unsigned to)
+{
+ if (!PageUptodate(page)) {
+ if (to - from != PAGE_CACHE_SIZE) {
+ void *kaddr = kmap_atomic(page, KM_USER0);
+ memset(kaddr, 0, from);
+ memset(kaddr + to, 0, PAGE_CACHE_SIZE - to);
+ flush_dcache_page(page);
+ kunmap_atomic(kaddr, KM_USER0);
+ }
+ SetPageUptodate(page);
+ }
This will mark the page uptodate while the piece between `to' and `from' is
uninitialised. A concurrent pagefault can come in and permit a read of
that uninitialised data. Because filemap_nopage() doesn't lock the page if
it is uptodate.
Okay - I snagged this code from fs/libfs.c (simple_prepare_write) --
is that code also not correct, or am I just using it in the wrong
context?
libfs.c is wrong. Nick has fixes, but they got tangled up in other stuff.
Yeah. 1/9 in that series should be applied on its own and sent upstream.
Need me to resend?
--
SUSE Labs, Novell Inc.
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