On Sat, Apr 18, 2015 at 04:37:35PM -0700, Kees Cook wrote: > On Mon, Apr 6, 2015 at 8:29 AM, Michael Kerrisk (man-pages) > <mtk.manpages@xxxxxxxxx> wrote: > > Hi Kees, > > > > I recently was asked about the point below, and had to go check the code > > to be sure, since the man page said nothing. It would be good to have > > a confirmation: the seccomp_data buffer supplied to a seccomp BPF program > > is read-only, right? (That is, one can't write to the buffer in order to > > change the arguments that a system call actually receives.) > > That's correct. If BPF even allows changing the data, it's not copied > back to the syscall when it runs. Anything wanting to do things like > that would need to use ptrace to catch the call an directly modify the > registers before continuing with the call. Today BPF programs can only read from seccomp_data buffer. I think it would be an interesting feature to allow overwrite of syscall arguments by the program on the fly... sometime in the future. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
