[PATCH 5.10 63/67] SMB3: fix readpage for large swap cache

Greg Kroah-Hartman
2021-08-02T14:03:58Z

From: Steve French <stfrench@microsoft.com>

commit f2a26a3cff27dfa456fef386fe5df56dcb4b47b6 upstream.

readpage was calculating the offset of the page incorrectly
for the case of large swapcaches.

loff_t offset = (loff_t)page->index << PAGE_SHIFT;

As pointed out by Matthew Wilcox, this needs to use
page_file_offset() to calculate the offset instead.
Pages coming from the swap cache have page->index set
to their index within the swapcache, not within the backing
file. For a sufficiently large swapcache, we could have
overlapping values of page->index within the same backing file.

Suggested by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: <stable@vger.kernel.org> # v5.7+
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/cifs/file.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -4550,7 +4550,7 @@ read_complete:

static int cifs_readpage(struct file *file, struct page *page)
{
- loff_t offset = (loff_t)page->index << PAGE_SHIFT;
+ loff_t offset = page_file_offset(page);
int rc = -EACCES;
unsigned int xid;