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Commit b403f0e3 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Al Viro
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9p: use file_dentry() 



v9fs may be used as lower layer of overlayfs and accessing f_path.dentry
can lead to a crash.  In this case it's a NULL pointer dereference in
p9_fid_create().

Fix by replacing direct access of file->f_path.dentry with the
file_dentry() accessor, which will always return a native object.

Reported-by: default avatarAlessio Igor Bogani <alessioigorbogani@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Tested-by: default avatarAlessio Igor Bogani <alessioigorbogani@gmail.com>
Fixes: 4bacc9c9 ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent b42b90d1

fs/9p/vfs_file.c

+3 −3
Original line number Diff line number Diff line
@@ -74,7 +74,7 @@ int v9fs_file_open(struct inode *inode, struct file *file) 
					v9fs_proto_dotu(v9ses));

	fid = file->private_data;

	if (!fid) {

		fid = v9fs_fid_clone(file->f_path.dentry);

		fid = v9fs_fid_clone(file_dentry(file));

		if (IS_ERR(fid))

			return PTR_ERR(fid);
@@ -100,7 +100,7 @@ int v9fs_file_open(struct inode *inode, struct file *file) 
		 * because we want write after unlink usecase

		 * to work.

		 */

		fid = v9fs_writeback_fid(file->f_path.dentry);

		fid = v9fs_writeback_fid(file_dentry(file));

		if (IS_ERR(fid)) {

			err = PTR_ERR(fid);

			mutex_unlock(&v9inode->v_mutex);
@@ -516,7 +516,7 @@ v9fs_mmap_file_mmap(struct file *filp, struct vm_area_struct *vma) 
		 * because we want write after unlink usecase

		 * to work.

		 */

		fid = v9fs_writeback_fid(filp->f_path.dentry);

		fid = v9fs_writeback_fid(file_dentry(filp));

		if (IS_ERR(fid)) {

			retval = PTR_ERR(fid);

			mutex_unlock(&v9inode->v_mutex);