NFSv4: Fix a problem whereby a buggy server can oops the kernel (d953126a) · Commits · 戴 / test

We just had a case in which a buggy server occasionally returns the wrong attributes during an OPEN call. While the client does catch this sort of condition in nfs4_open_done(), and causes the nfs4_atomic_open() to return -EISDIR, the logic in nfs_atomic_lookup() is broken, since it causes a fallback to an ordinary lookup instead of just returning the error. When the buggy server then returns a regular file for the fallback lookup, the VFS allows the open, and bad things start to happen, since the open file doesn't have any associated NFSv4 state. The fix is firstly to return the EISDIR/ENOTDIR errors immediately, and secondly to ensure that we are always careful when dereferencing the nfs_open_context state pointer. Signed-off-by:

Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/dir.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1025,12 +1025,12 @@ static struct dentry nfs_atomic_lookup(struct inode dir, struct dentry *dentry
		res = NULL;
		goto out;
		/* This turned out not to be a regular file */
		case -EISDIR:
		case -ENOTDIR:
		goto no_open;
		case -ELOOP:
		if (!(nd->intent.open.flags & O_NOFOLLOW))
		goto no_open;
		/* case -EISDIR: */
		/* case -EINVAL: */
		default:
		goto out;

fs/nfs/nfs4proc.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -4093,15 +4093,23 @@ nfs4_proc_lock(struct file filp, int cmd, struct file_lock request)
		if (request->fl_start < 0 \|\| request->fl_end < 0)
		return -EINVAL;

		if (IS_GETLK(cmd))
		if (IS_GETLK(cmd)) {
		if (state != NULL)
		return nfs4_proc_getlk(state, F_GETLK, request);
		return 0;
		}

		if (!(IS_SETLK(cmd) \|\| IS_SETLKW(cmd)))
		return -EINVAL;

		if (request->fl_type == F_UNLCK)
		if (request->fl_type == F_UNLCK) {
		if (state != NULL)
		return nfs4_proc_unlck(state, cmd, request);
		return 0;
		}

		if (state == NULL)
		return -ENOLCK;
		do {
		status = nfs4_proc_setlk(state, cmd, request);
		if ((status != -EAGAIN) \|\| IS_SETLK(cmd))

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