Quoting Will Drewry (wad@xxxxxxxxxxxx): > [This patch depends on luto@xxxxxxx's no_new_privs patch: > https://lkml.org/lkml/2012/1/12/446 > ] > > This patch adds support for seccomp mode 2. This mode enables dynamic > enforcement of system call filtering policy in the kernel as specified > by a userland task. The policy is expressed in terms of a Berkeley > Packet Filter program, as is used for userland-exposed socket filtering. > Instead of network data, the BPF program is evaluated over struct > seccomp_filter_data at the time of the system call. > > A filter program may be installed by a userland task by calling > prctl(PR_ATTACH_SECCOMP_FILTER, &fprog); > where fprog is of type struct sock_fprog. > > If the first filter program allows subsequent prctl(2) calls, then > additional filter programs may be attached. All attached programs > must be evaluated before a system call will be allowed to proceed. > > To avoid CONFIG_COMPAT related landmines, once a filter program is > installed using specific is_compat_task() value, it is not allowed to > make system calls using the alternate entry point. > > Filter programs will be inherited across fork/clone and execve, however > the installation of filters must be preceded by setting 'no_new_privs' > to ensure that unprivileged tasks cannot attach filters that affect > privileged tasks (e.g., setuid binary). Tasks with CAP_SYS_ADMIN > in their namespace may install inheritable filters without setting > the no_new_privs bit. > > There are a number of benefits to this approach. A few of which are > as follows: > - BPF has been exposed to userland for a long time. > - Userland already knows its ABI: system call numbers and desired > arguments > - No time-of-check-time-of-use vulnerable data accesses are possible. > - system call arguments are loaded on demand only to minimize copying > required for system call number-only policy decisions. > > This patch includes its own BPF evaluator, but relies on the > net/core/filter.c BPF checking code. It is possible to share > evaluators, but the performance sensitive nature of the network > filtering path makes it an iterative optimization which (I think :) can > be tackled separately via separate patchsets. (And at some point sharing > BPF JIT code!) > > v6: - fix memory leak on attach compat check failure > - require no_new_privs || CAP_SYS_ADMIN prior to filter > installation. (luto@xxxxxxx) > - s/seccomp_struct_/seccomp_/ for macros/functions > (amwang@xxxxxxxxxx) > - cleaned up Kconfig (amwang@xxxxxxxxxx) > - on block, note if the call was compat (so the # means something) > v5: - uses syscall_get_arguments > (indan@xxxxxx,oleg@xxxxxxxxxx, mcgrathr@xxxxxxxxxxxx) > - uses union-based arg storage with hi/lo struct to > handle endianness. Compromises between the two alternate > proposals to minimize extra arg shuffling and account for > endianness assuming userspace uses offsetof(). > (mcgrathr@xxxxxxxxxxxx, indan@xxxxxx) > - update Kconfig description > - add include/seccomp_filter.h and add its installation > - (naive) on-demand syscall argument loading > - drop seccomp_t (eparis@xxxxxxxxxx) > v4: - adjusted prctl to make room for PR_[SG]ET_NO_NEW_PRIVS > - now uses current->no_new_privs > (luto@xxxxxxx,torvalds@xxxxxxxxxxxxxxxxxxxx) > - assign names to seccomp modes (rdunlap@xxxxxxxxxxxx) > - fix style issues (rdunlap@xxxxxxxxxxxx) > - reworded Kconfig entry (rdunlap@xxxxxxxxxxxx) > v3: - macros to inline (oleg@xxxxxxxxxx) > - init_task behavior fixed (oleg@xxxxxxxxxx) > - drop creator entry and extra NULL check (oleg@xxxxxxxxxx) > - alloc returns -EINVAL on bad sizing (serge.hallyn@xxxxxxxxxxxxx) > - adds tentative use of "always_unprivileged" as per > torvalds@xxxxxxxxxxxxxxxxxxxx and luto@xxxxxxx > v2: - (patch 2 only) > > Signed-off-by: Will Drewry <wad@xxxxxxxxxxxx> Hi Will, as far as I can tell based on changelog I suspect you could have kept my Acked-by (from v3?). However, I'll wait until your next submission (as I see there were a few change requests), and do a final complete new review of that. Thanks for continuing to push on this. -serge -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
