afs: Fix the maths in afs_fs_store_data()

[ Upstream commit 146a119 ] afs_fs_store_data() works out of the size of the write it's going to make, but it uses 32-bit unsigned subtraction in one place that gets automatically cast to loff_t. However, if to < offset, then the number goes negative, but as the result isn't signed, this doesn't get sign-extended to 64-bits when placed in a loff_t. Fix by casting the operands to loff_t. Signed-off-by: David Howells <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
corrosion · Dec 20, 2017 · fa03453 · fa03453
1 parent 1efae6c
commit fa03453
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
@@ -1225,7 +1225,7 @@ int afs_fs_store_data(struct afs_server *server, struct afs_writeback *wb,
 	_enter(",%x,{%x:%u},,",
 	       key_serial(wb->key), vnode->fid.vid, vnode->fid.vnode);
 
-	size = to - offset;
+	size = (loff_t)to - (loff_t)offset;
 	if (first != last)
 		size += (loff_t)(last - first) << PAGE_SHIFT;
 	pos = (loff_t)first << PAGE_SHIFT;