Merge tag 'iomap-4.21-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

Pull iomap update from Darrick Wong:
 "Fix a memory overflow bug for blocksize < pagesize"

* tag 'iomap-4.21-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  iomap: don't search past page end in iomap_is_partially_uptodate

1 files changed, 15 insertions, 2 deletions

diff --git a/fs/iomap.c b/fs/iomap.c
index d6bc98ae8d35..ce837d962d47 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -492,16 +492,29 @@ done:
 }
 EXPORT_SYMBOL_GPL(iomap_readpages);
 
+/*
+ * iomap_is_partially_uptodate checks whether blocks within a page are
+ * uptodate or not.
+ *
+ * Returns true if all blocks which correspond to a file portion
+ * we want to read within the page are uptodate.
+ */
 int
 iomap_is_partially_uptodate(struct page *page, unsigned long from,
                 unsigned long count)
 {
         struct iomap_page *iop = to_iomap_page(page);
         struct inode *inode = page->mapping->host;
-        unsigned first = from >> inode->i_blkbits;
-        unsigned last = (from + count - 1) >> inode->i_blkbits;
+        unsigned len, first, last;
         unsigned i;
 
+        /* Limit range to one page */
+        len = min_t(unsigned, PAGE_SIZE - from, count);
+
+        /* First and last blocks in range within page */
+        first = from >> inode->i_blkbits;
+        last = (from + len - 1) >> inode->i_blkbits;
+
         if (iop) {
                 for (i = first; i <= last; i++)
                         if (!test_bit(i, iop->uptodate))