mm: fix XIP file writes

Writing to XIP files at a non-page-aligned offset results in data corruption
because the writes were always sent to the start of the page.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
index 32132f3..e233fff 100644 (file)
--- a/mm/filemap_xip.c
+++ b/mm/filemap_xip.c
@@ -314,7 +314,7 @@ __xip_file_write(struct file *filp, const char __user *buf,
                fault_in_pages_readable(buf, bytes);
                kaddr = kmap_atomic(page, KM_USER0);
                copied = bytes -
-                       __copy_from_user_inatomic_nocache(kaddr, buf, bytes);
+                       __copy_from_user_inatomic_nocache(kaddr + offset, buf, bytes);
                kunmap_atomic(kaddr, KM_USER0);
                flush_dcache_page(page);