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Commit 90478939 authored by Jeff Layton's avatar Jeff Layton
Browse files

locks: require that flock->l_pid be set to 0 for file-private locks 



Neil Brown suggested potentially overloading the l_pid value as a "lock
context" field for file-private locks. While I don't think we will
probably want to do that here, it's probably a good idea to ensure that
in the future we could extend this API without breaking existing
callers.

Typically the l_pid value is ignored for incoming struct flock
arguments, serving mainly as a place to return the pid of the owner if
there is a conflicting lock. For file-private locks, require that it
currently be set to 0 and return EINVAL if it isn't. If we eventually
want to make a non-zero l_pid mean something, then this will help ensure
that we don't break legacy programs that are using file-private locks.

Cc: Neil Brown <neilb@suse.de>
Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
parent 5d50ffd7

fs/locks.c

+24 −0
Original line number Diff line number Diff line
@@ -1931,6 +1931,10 @@ int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock __user *l) 
		goto out;



	if (cmd == F_GETLKP) {

		error = -EINVAL;

		if (flock.l_pid != 0)

			goto out;



		cmd = F_GETLK;

		file_lock.fl_flags |= FL_FILE_PVT;

		file_lock.fl_owner = (fl_owner_t)filp;
@@ -2062,11 +2066,19 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd, 
	 */

	switch (cmd) {

	case F_SETLKP:

		error = -EINVAL;

		if (flock.l_pid != 0)

			goto out;



		cmd = F_SETLK;

		file_lock->fl_flags |= FL_FILE_PVT;

		file_lock->fl_owner = (fl_owner_t)filp;

		break;

	case F_SETLKPW:

		error = -EINVAL;

		if (flock.l_pid != 0)

			goto out;



		cmd = F_SETLKW;

		file_lock->fl_flags |= FL_FILE_PVT;

		file_lock->fl_owner = (fl_owner_t)filp;
@@ -2121,6 +2133,10 @@ int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 __user *l) 
		goto out;



	if (cmd == F_GETLKP) {

		error = -EINVAL;

		if (flock.l_pid != 0)

			goto out;



		cmd = F_GETLK64;

		file_lock.fl_flags |= FL_FILE_PVT;

		file_lock.fl_owner = (fl_owner_t)filp;
@@ -2185,11 +2201,19 @@ int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd, 
	 */

	switch (cmd) {

	case F_SETLKP:

		error = -EINVAL;

		if (flock.l_pid != 0)

			goto out;



		cmd = F_SETLK64;

		file_lock->fl_flags |= FL_FILE_PVT;

		file_lock->fl_owner = (fl_owner_t)filp;

		break;

	case F_SETLKPW:

		error = -EINVAL;

		if (flock.l_pid != 0)

			goto out;



		cmd = F_SETLKW64;

		file_lock->fl_flags |= FL_FILE_PVT;

		file_lock->fl_owner = (fl_owner_t)filp;