[PATCH 5.14 026/151] ovl: fix IOCB_DIRECT if underlying fs doesnt support direct IO

Greg Kroah-Hartman
2021-10-11T14:00:50Z

From: Miklos Szeredi <mszeredi@redhat.com>

commit 1dc1eed46f9fa4cb8a07baa24fb44c96d6dd35c9 upstream.

Normally the check at open time suffices, but e.g loop device does set
IOCB_DIRECT after doing its own checks (which are not sufficent for
overlayfs).

Make sure we don't call the underlying filesystem read/write method with
the IOCB_DIRECT if it's not supported.

Reported-by: Huang Jianan <huangjianan@oppo.com>
Fixes: 16914e6fc7e1 ("ovl: add ovl_read_iter()")
Cc: <stable@vger.kernel.org> # v4.19
Tested-by: Huang Jianan <huangjianan@oppo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/overlayfs/file.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -296,6 +296,12 @@ static ssize_t ovl_read_iter(struct kioc
if (ret)
return ret;

+ ret = -EINVAL;
+ if (iocb->ki_flags & IOCB_DIRECT &&
+ (!real.file->f_mapping->a_ops ||
+ !real.file->f_mapping->a_ops->direct_IO))
+ goto out_fdput;
+
old_cred = ovl_override_creds(file_inode(file)->i_sb);
if (is_sync_kiocb(iocb)) {
ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
@@ -320,7 +326,7 @@ static ssize_t ovl_read_iter(struct kioc
out:
revert_creds(old_cred);
ovl_file_accessed(file);
-
+out_fdput:
fdput(real);

return ret;
@@ -349,6 +355,12 @@ static ssize_t ovl_write_iter(struct kio
if (ret)
goto out_unlock;

+ ret = -EINVAL;
+ if (iocb->ki_flags & IOCB_DIRECT &&
+ (!real.file->f_mapping->a_ops ||
+ !real.file->f_mapping->a_ops->direct_IO))
+ goto out_fdput;
+
if (!ovl_should_sync(OVL_FS(inode->i_sb)))
ifl &= ~(IOCB_DSYNC | IOCB_SYNC);

@@ -384,6 +396,7 @@ static ssize_t ovl_write_iter(struct kio
}
out:
revert_creds(old_cred);
+out_fdput:
fdput(real);