Commit cf01f4ee authored by Jeff Layton's avatar Jeff Layton
Browse files

locks: only validate the lock vs. f_mode in F_SETLK codepaths 



v2: replace missing break in switch statement (as pointed out by Dave
    Jones)

commit bce7560d (locks: consolidate checks for compatible
filp->f_mode values in setlk handlers) introduced a regression in the
F_GETLK handler.

flock64_to_posix_lock is a shared codepath between F_GETLK and F_SETLK,
but the f_mode checks should only be applicable to the F_SETLK codepaths
according to POSIX.

Instead of just reverting the patch, add a new function to do this
checking and have the F_SETLK handlers call it.

Cc: Dave Jones <davej@redhat.com>
Reported-and-Tested-by: default avatarReuben Farrelly <reuben@reub.net>
Signed-off-by: default avatarJeff Layton <jlayton@poochiereds.net>
parent afcf0a2d

fs/locks.c

+24 −12
Original line number Diff line number Diff line
@@ -389,18 +389,6 @@ static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl, 
	fl->fl_ops = NULL;

	fl->fl_lmops = NULL;



	/* Ensure that fl->fl_filp has compatible f_mode */

	switch (l->l_type) {

	case F_RDLCK:

		if (!(filp->f_mode & FMODE_READ))

			return -EBADF;

		break;

	case F_WRLCK:

		if (!(filp->f_mode & FMODE_WRITE))

			return -EBADF;

		break;

	}



	return assign_type(fl, l->l_type);

}
@@ -2034,6 +2022,22 @@ static int do_lock_file_wait(struct file *filp, unsigned int cmd, 
	return error;

}



/* Ensure that fl->fl_filp has compatible f_mode for F_SETLK calls */

static int

check_fmode_for_setlk(struct file_lock *fl)

{

	switch (fl->fl_type) {

	case F_RDLCK:

		if (!(fl->fl_file->f_mode & FMODE_READ))

			return -EBADF;

		break;

	case F_WRLCK:

		if (!(fl->fl_file->f_mode & FMODE_WRITE))

			return -EBADF;

	}

	return 0;

}



/* Apply the lock described by l to an open file descriptor.

 * This implements both the F_SETLK and F_SETLKW commands of fcntl().

 */
@@ -2071,6 +2075,10 @@ again: 
	if (error)

		goto out;



	error = check_fmode_for_setlk(file_lock);

	if (error)

		goto out;



	/*

	 * If the cmd is requesting file-private locks, then set the

	 * FL_OFDLCK flag and override the owner.
@@ -2206,6 +2214,10 @@ again: 
	if (error)

		goto out;



	error = check_fmode_for_setlk(file_lock);

	if (error)

		goto out;



	/*

	 * If the cmd is requesting file-private locks, then set the

	 * FL_OFDLCK flag and override the owner.

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