On Thu, Aug 1, 2013 at 4:36 AM, Rich Felker <dalias@xxxxxxxxxx> wrote: > On Thu, Aug 01, 2013 at 01:29:51AM -0700, Christoph Hellwig wrote: >> Btw, FreeBSD has an extension to shm_open to create unnamed but fd >> passable segments. From their man page: >> >> As a FreeBSD extension, the constant SHM_ANON may be used for the path >> argument to shm_open(). In this case, an anonymous, unnamed shared >> memory object is created. Since the object has no name, it cannot be >> removed via a subsequent call to shm_unlink(). Instead, the shared >> memory object will be garbage collected when the last reference to the >> shared memory object is removed. The shared memory object may be shared >> with other processes by sharing the file descriptor via fork(2) or >> sendmsg(2). Attempting to open an anonymous shared memory object with >> O_RDONLY will fail with EINVAL. All other flags are ignored. >> >> To me this sounds like the best way to expose this functionality to the >> user. Implementing it is another question as shm_open sits in libc, >> we could either take it and shm_unlink to the kernel, or use O_TMPFILE >> on tmpfs as the backend. > > I'm not sure what the purpose is. shm_open with a long random filename > and O_EXCL|O_CREAT, followed immediately by shm_unlink, is just as > good except in the case where you have a malicious user killing the > process in between these two operations. Practically, filename length is restricted by NAME_MAX(255bytes). Several people don't think it is enough long length. The point is, race free API. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>