On Thu, May 22, 2014 at 4:05 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > Applying restrictive seccomp filter programs to large or diverse > codebases often requires handling threads which may be started early in > the process lifetime (e.g., by code that is linked in). While it is > possible to apply permissive programs prior to process start up, it is > difficult to further restrict the kernel ABI to those threads after that > point. > > This change adds a new seccomp extension action for synchronizing thread > group seccomp filters and a prctl() for accessing that functionality, > as well as a flag for SECCOMP_EXT_ACT_FILTER to perform sync at filter > installation time. > > When calling prctl(PR_SECCOMP_EXT, SECCOMP_EXT_ACT, SECCOMP_EXT_ACT_FILTER, > flags, filter) with flags containing SECCOMP_FILTER_TSYNC, or when calling > prctl(PR_SECCOMP_EXT, SECCOMP_EXT_ACT, SECCOMP_EXT_ACT_TSYNC, 0, 0), it > will attempt to synchronize all threads in current's threadgroup to its > seccomp filter program. This is possible iff all threads are using a filter > that is an ancestor to the filter current is attempting to synchronize to. > NULL filters (where the task is running as SECCOMP_MODE_NONE) are also > treated as ancestors allowing threads to be transitioned into > SECCOMP_MODE_FILTER. If prctrl(PR_SET_NO_NEW_PRIVS, ...) has been set on the > calling thread, no_new_privs will be set for all synchronized threads too. > On success, 0 is returned. On failure, the pid of one of the failing threads > will be returned, with as many filters installed as possible. Is there a use case for adding a filter and synchronizing filters being separate operations? If not, I think this would be easier to understand and to use if there was just a single operation. If you did that, you'd have to decide whether to continue requiring that all the other threads have a filter that's an ancestor of the current thread's filter. --Andy -- 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
