ext4: teach ext4_ext_find_extent() to free path on error
Right now, there are a places where it is all to easy to leak memory
on an error path, via a usage like this:
struct ext4_ext_path *path = NULL
while (...) {
...
path = ext4_ext_find_extent(inode, block, path, 0);
if (IS_ERR(path)) {
/* oops, if path was non-NULL before the call to
ext4_ext_find_extent, we've leaked it! :-( */
...
return PTR_ERR(path);
}
...
}
Unfortunately, there some code paths where we are doing the following
instead:
path = ext4_ext_find_extent(inode, block, orig_path, 0);
and where it's important that we _not_ free orig_path in the case
where ext4_ext_find_extent() returns an error.
So change the function signature of ext4_ext_find_extent() so that it
takes a struct ext4_ext_path ** for its third argument, and by
default, on an error, it will free the struct ext4_ext_path, and then
zero out the struct ext4_ext_path * pointer. In order to avoid
causing problems, we add a flag EXT4_EX_NOFREE_ON_ERR which causes
ext4_ext_find_extent() to use the original behavior of forcing the
caller to deal with freeing the original path pointer on the error
case.
The goal is to get rid of EXT4_EX_NOFREE_ON_ERR entirely, but this
allows for a gentle transition and makes the patches easier to verify.
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index c8f895b..5e2465a 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -37,7 +37,7 @@
int ret = 0;
struct ext4_ext_path *path;
- path = ext4_ext_find_extent(inode, lblock, *orig_path, EXT4_EX_NOCACHE);
+ path = ext4_ext_find_extent(inode, lblock, orig_path, EXT4_EX_NOCACHE);
if (IS_ERR(path))
ret = PTR_ERR(path);
else if (path[ext_depth(inode)].p_ext == NULL)