Re: [PATCH][next] btrfs: fix memory leak of path on error return path

[Anand Jain]

On 5/7/19 12:37 AM, David Sterba wrote:
> On Tue, Jul 02, 2019 at 03:10:28PM +0100, Colin King wrote:
> > From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> >
> > Currently if the allocation of roots or tmp_ulist fails the error handling
> > does not free up the allocation of path causing a memory leak. Fix this by
> > freeing path with a call to btrfs_free_path before taking the error return
> > path.
> >
> > Addresses-Coverity: ("Resource leak")
>
> Does this have an id, that coverity uses?
>
> > Fixes: 5911c8fe05c5 ("btrfs: fiemap: preallocate ulists for btrfs_check_shared")
> > Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > ---
> >   fs/btrfs/extent_io.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> > index 1eb671c16ff1..d7f37a33d597 100644
> > --- a/fs/btrfs/extent_io.c
> > +++ b/fs/btrfs/extent_io.c
> > @@ -4600,6 +4600,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> >   	tmp_ulist = ulist_alloc(GFP_KERNEL);
> >   	if (!roots || !tmp_ulist) {
> >   		ret = -ENOMEM;
> > +		btrfs_free_path(path);
>
> This fixes only one leak, therere are more that I spotted while
> reviewing this patch. The gotos from the while-loop jump to
> out_free_list but that leave the path behind.
>
> That's why the exit block is a better place for the cleanups. This
> requires proper nesting of the cleanup calls, that's slightly
> inconvenient in this case. The free_path is before call to
> unlock_extent_cached so when the ordre is switched and free_path moved
> to out_free_ulist, then all the leaks are addressed in one go.
>
> Bummer that the leaks escaped sight of original patch author (me), 2
> reviewers and now 1 fix reviewer.

There is no goto out_free_ulist inside the while loop; where do you see
that? I did git pull again and checked.

4664         while (!end) {
::
4726                                 goto out_free;
::
4748                         goto out;
::
4759                         goto out_free;
::
4761         }