Commit eaa2b82c authored by NeilBrown's avatar NeilBrown Committed by Anna Schumaker

NFS: guard against confused server in nfs_atomic_open()

A confused server could return a filehandle for an
NFSv4 OPEN request, which it previously returned for a directory.
So the inode returned by  ->open_context() in nfs_atomic_open()
could conceivably be a directory inode.

This has particular implications for the call to
nfs_file_set_open_context() in nfs_finish_open().
If that is called on a directory inode, then the nfs_open_context
that gets stored in the filp->private_data will be linked to
nfs_inode->open_files.

When the directory is closed, nfs_closedir() will (ultimately)
free the ->private_data, but not unlink it from nfs_inode->open_files
(because it doesn't expect an nfs_open_context there).

Subsequently the memory could get used for something else and eventually
if the ->open_files list is walked, the walker will fall off the end and
crash.

So: change nfs_finish_open() to only call nfs_file_set_open_context()
for regular-file inodes.

This failure mode has been seen in a production setting (unknown NFS
server implementation).  The kernel was v3.0 and the specific sequence
seen would not affect more recent kernels, but I think a risk is still
present, and caution is wise.
Signed-off-by: default avatarNeilBrown <neilb@suse.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent cc89684c
...@@ -1431,8 +1431,10 @@ static int nfs_finish_open(struct nfs_open_context *ctx, ...@@ -1431,8 +1431,10 @@ static int nfs_finish_open(struct nfs_open_context *ctx,
err = finish_open(file, dentry, do_open, opened); err = finish_open(file, dentry, do_open, opened);
if (err) if (err)
goto out; goto out;
if (S_ISREG(file->f_path.dentry->d_inode->i_mode))
nfs_file_set_open_context(file, ctx); nfs_file_set_open_context(file, ctx);
else
err = -ESTALE;
out: out:
return err; return err;
} }
......
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