On Wed, Sep 22, 2021 at 04:00:47PM +0200, Miklos Szeredi wrote:
> First let's fix the oops: ovl_read_iter()/ovl_write_iter() must check
> real file's ->direct_IO if IOCB_DIRECT is set in iocb->ki_flags and
> return -EINVAL if not.
And here's that fix. Please test.
Thanks,
Miklos
---
From: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Subject: ovl: fix IOCB_DIRECT if underlying fs doesn't support direct IO
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@xxxxxxxx>
Fixes: 16914e6fc7e1 ("ovl: add ovl_read_iter()")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.19
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
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);
out_unlock:
