Hi Andy, On 05/19/2015 07:21 PM, Andy Lutomirski wrote: > On Tue, May 19, 2015 at 12:56 AM, Michael Kerrisk (man-pages) > <mtk.manpages@xxxxxxxxx> wrote: >> Hi Andy, >> >> Thanks for this patch. There are some broken pieces though. Also, >> I have some minor questions about the API design. See below. >> >> On 05/15/2015 08:43 AM, Andy Lutomirski wrote: >>> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx> >>> --- >>> >>> There was no v1. I'm calling this v2 to keep it in sync with the kernel >>> patch versioning. >>> >>> man2/prctl.2 | 10 ++++++++++ >>> man7/capabilities.7 | 32 ++++++++++++++++++++++++++------ >>> 2 files changed, 36 insertions(+), 6 deletions(-) >>> >>> diff --git a/man2/prctl.2 b/man2/prctl.2 >>> index b352f6283624..5861e3aefe9a 100644 >>> --- a/man2/prctl.2 >>> +++ b/man2/prctl.2 >>> @@ -949,6 +949,16 @@ had been called. >>> For further information on Intel MPX, see the kernel source file >>> .IR Documentation/x86/intel_mpx.txt . >>> .\" >>> +.TP >>> +.BR PR_CAP_AMBIENT " (since Linux 4.2)" >>> +Reads or changes the ambient capability set. If arg2 is PR_CAP_AMBIENT_RAISE, >>> +then the capability specified in arg3 is added to the ambient set. This will >>> +fail, returning EPERM, if the capability is not already both permitted and >>> +inheritable or if the SECBIT_NO_CAP_AMBIENT_RAISE securebit is set. If arg2 >>> +is PR_CAP_AMBIENT_LOWER, then the capability specified in arg3 is removed >>> +from the ambient set. If arg2 is PR_CAP_AMBIENT_GET, then >>> +.BR prctl (2) >>> +will return 1 if the capability in arg3 is in the ambient set and 0 if not. >> >> Some API design questions: >> >> 1. We already have prctl() operations that work on some capability sets: >> PR_CAPBSET_READ and PR_CAPBSET_DROP. These don't use arg3; the operation >> is directly encoded in the first argument of prctl(). Just to keep some >> consistency, why not do things the same way for these new operations? > > I'm torn. On the one hand, consistency is nice. On the other hand, > prctl is a mess Agreed. > and trying to organize new additions seems like a good > idea. Sure, but what is your organizing principle here? (I don't feel strongly about it, but it's not clear to me what trumps the (mild) degree of consistency that I suggest.) >> Also, you could opt for some consistency in the naming, so using "READ" >> rather than "GET", for example. On the other hand, both "READ" and "GET" >> are suboptimal names: this is really a test operation. So, maybe a >> clean break to a good name, PR_CAP_AMBIENT_IS_SET, is best? > > I like IS_SET. Okay. >> Thus: >> >> prctl(PR_CAP_AMBIENT_READ, cap, 0, 0, 0); // or PR_CAP_AMBIENT_IS_SET? >> prctl(PR_CAP_AMBIENT_RAISE, cap, 0, 0, 0); >> prctl(PR_CAP_AMBIENT_LOWER, cap, 0, 0, 0); >> >> 2. In terms of the API design, would it be useful to have a prctl() operation >> that clears the entire ambient set? >> >> prctl(PR_CAP_AMBIENT_ZERO, 0, 0, 0, 0); // or PR_CAP_AMBIENT_EMPTY? > > Seems like a good idea. How about _CLEAR? Also good. [...] Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- 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
