On Sat, Feb 25, 2012 at 2:20 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > On Fri, Feb 24, 2012 at 7:21 PM, Will Drewry <wad@xxxxxxxxxxxx> wrote: >> This change adds the SECCOMP_RET_ERRNO as a valid return value from a >> seccomp filter. Additionally, it makes the first use of the lower >> 16-bits for storing a filter-supplied errno. 16-bits is more than >> enough for the errno-base.h calls. >> >> Returning errors instead of immediately terminating processes that >> violate seccomp policy allow for broader use of this functionality >> for kernel attack surface reduction. For example, a linux container >> could maintain a whitelist of pre-existing system calls but drop >> all new ones with errnos. This would keep a logically static attack >> surface while providing errnos that may allow for graceful failure >> without the downside of do_exit() on a bad call. >> >> v11: - check for NULL filter (keescook@xxxxxxxxxxxx) >> v10: - change loaders to fn >> v9: - n/a >> v8: - update Kconfig to note new need for syscall_set_return_value. >> - reordered such that TRAP behavior follows on later. >> - made the for loop a little less indent-y >> v7: - introduced >> >> Signed-off-by: Will Drewry <wad@xxxxxxxxxxxx> > > Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Thanks! >> + /* Ensure unexpected behavior doesn't result in failing open. */ >> + if (unlikely(current->seccomp.filter == NULL)) >> + ret = SECCOMP_RET_KILL; > > Any reason to not just immediately return in this case? Not that I can think of. I can just have it bail here. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
