On Sat, 2018-03-17 at 15:05 +0000, Al Viro wrote: > On Sat, Mar 17, 2018 at 10:25:20AM -0400, Jeff Layton wrote: > > From: Jeff Layton <jlayton@xxxxxxxxxx> > > > > POSIX mandates that open fds and their associated file locks should be > > preserved across an execve. This works, unless the process is > > multithreaded at the time that execve is called. > > > > In that case, we'll end up unsharing the files_struct but the locks will > > still have their fl_owner set to the address of the old one. Eventually, > > when the other threads die and the last reference to the old > > files_struct is put, any POSIX locks get torn down since it looks like > > a close occurred on them. > > > > The result is that all of your open files will be intact with none of > > the locks you held before execve. The simple answer to this is "use OFD > > locks", but this is a nasty surprise and it violates the spec. > > > > On a successful execve, change ownership of any POSIX file_locks > > associated with the old files_struct to the new one, if we ended up > > swapping it out. > > TBH, I don't like the way you implement that. Why not simply use > iterate_fd()? Ahh, I wasn't aware of it. I copied the loop in change_lock_owners from close_files. I'll have a look at iterate_fd(). Thanks, -- Jeff Layton <jlayton@xxxxxxxxxx>
