ovl: fix incorrect fdput() on aio completion

commit 724768a39374d35b70eaeae8dd87048a2ec7ae8e upstream.

ovl_{read,write}_iter() always call fdput(real) to put one or zero
refcounts of the real file, but for aio, whether it was submitted or not,
ovl_aio_put() also calls fdput(), which is not balanced.  This is only a
problem in the less common case when FDPUT_FPUT flag is set.

To fix the problem use get_file() to take file refcount and use fput()
instead of fdput() in ovl_aio_put().

Fixes: 2406a307ac7d ("ovl: implement async IO routines")
Cc: <stable@vger.kernel.org> # v5.6
Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 6011f955436ba7771800fac36abf6a88cd8cc094..cc0c077165bde142ed23d8c42b86e4e4b9ec7182 100644 (file)
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -19,7 +19,6 @@ struct ovl_aio_req {
        struct kiocb iocb;
        refcount_t ref;
        struct kiocb *orig_iocb;
-       struct fd fd;
 };
 
 static struct kmem_cache *ovl_aio_request_cachep;
@@ -260,7 +259,7 @@ static rwf_t ovl_iocb_to_rwf(int ifl)
 static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
 {
        if (refcount_dec_and_test(&aio_req->ref)) {
-               fdput(aio_req->fd);
+               fput(aio_req->iocb.ki_filp);
                kmem_cache_free(ovl_aio_request_cachep, aio_req);
        }
 }
@@ -325,10 +324,9 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
                if (!aio_req)
                        goto out;
 
-               aio_req->fd = real;
                real.flags = 0;
                aio_req->orig_iocb = iocb;
-               kiocb_clone(&aio_req->iocb, iocb, real.file);
+               kiocb_clone(&aio_req->iocb, iocb, get_file(real.file));
                aio_req->iocb.ki_complete = ovl_aio_rw_complete;
                refcount_set(&aio_req->ref, 2);
                ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
@@ -396,10 +394,9 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
                /* Pacify lockdep, same trick as done in aio_write() */
                __sb_writers_release(file_inode(real.file)->i_sb,
                                     SB_FREEZE_WRITE);
-               aio_req->fd = real;
                real.flags = 0;
                aio_req->orig_iocb = iocb;
-               kiocb_clone(&aio_req->iocb, iocb, real.file);
+               kiocb_clone(&aio_req->iocb, iocb, get_file(real.file));
                aio_req->iocb.ki_flags = ifl;
                aio_req->iocb.ki_complete = ovl_aio_rw_complete;
                refcount_set(&aio_req->ref, 2);