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

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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: Jeff Layton <jlayton@redhat.com>
This commit is contained in:
Jeff Layton 2014-03-04 10:30:23 -05:00
parent 5d50ffd7c3
commit 90478939dc
1 changed files with 24 additions and 0 deletions
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24
fs/locks.c
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@ -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 @@ again:
*/
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 @@ again:
*/
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;