On Wed, Sep 30, 2015 at 11:55 AM, Tycho Andersen <tycho.andersen@xxxxxxxxxxxxx> wrote: > On Wed, Sep 30, 2015 at 11:47:05AM -0700, Andy Lutomirski wrote: >> On Wed, Sep 30, 2015 at 11:41 AM, Tycho Andersen >> <tycho.andersen@xxxxxxxxxxxxx> wrote: >> > On Wed, Sep 30, 2015 at 11:25:41AM -0700, Andy Lutomirski wrote: >> >> On Wed, Sep 30, 2015 at 11:13 AM, Tycho Andersen >> >> <tycho.andersen@xxxxxxxxxxxxx> wrote: >> >> > This command allows comparing the underling private data of two fds. This >> >> > is useful e.g. to find out if a seccomp filter is inherited, since struct >> >> > seccomp_filter are unique across tasks and are the private_data seccomp >> >> > fds. >> >> >> >> This is very implementation-specific and may have nasty ABI >> >> consequences far outside seccomp. Let's do something specific to >> >> seccomp and/or eBPF. >> > >> > We could change the name to a less generic KCMP_SECCOMP_FD or >> > something, but without some sort of GUID on each struct >> > seccomp_filter, the implementation would be effectively the same as it >> > is today. Is that enough, or do we need a GUID? >> > >> >> I don't care about the GUID. I think we should name it >> KCMP_SECCOMP_FD and make it only work on seccomp fds. > > Ok, I can do that. > >> Alternatively, we could figure out why KCMP_FILE doesn't do the trick >> and consider fixing it. IMO it's really too bad that struct file is >> so heavyweight that we can't really just embed one in all kinds of >> structures. > > The problem is that KCMP_FILE compares the file objects themselves, > instead of the underlying data. If I ask for a seccomp fd for filter 0 > twice, I'll have two different file objects and they won't be equal. I > suppose we could add some special logic inside KCMP_FILE to compare > the underlying data in special cases (seccomp, ebpf, others?), but it > seems cleaner to have a separate command as you described above. > What I meant was that maybe we could get the two requests to actually produce the same struct file. But that could get very messy memory-wise. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
