On Thu, Sep 24, 2020 at 1:29 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote: > This emulates absolutely the most basic seccomp filters to figure out > if they will always give the same results for a given arch/nr combo. > > Nearly all seccomp filters are built from the following ops: > > BPF_LD | BPF_W | BPF_ABS > BPF_JMP | BPF_JEQ | BPF_K > BPF_JMP | BPF_JGE | BPF_K > BPF_JMP | BPF_JGT | BPF_K > BPF_JMP | BPF_JSET | BPF_K > BPF_JMP | BPF_JA > BPF_RET | BPF_K > > These are now emulated to check for accesses beyond seccomp_data::arch > or unknown instructions. > > Not yet implemented are: > > BPF_ALU | BPF_AND (generated by libseccomp and Chrome) BPF_AND is normally only used on syscall arguments, not on the syscall number or the architecture, right? And when a syscall argument is loaded, we abort execution anyway. So I think there is no need to implement those? > Suggested-by: Jann Horn <jannh@xxxxxxxxxx> > Link: https://lore.kernel.org/lkml/CAG48ez1p=dR_2ikKq=xVxkoGg0fYpTBpkhJSv1w-6BG=76PAvw@xxxxxxxxxxxxxx/ > Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> > --- > kernel/seccomp.c | 82 ++++++++++++++++++++++++++++++++++++++++++++--- > net/core/filter.c | 3 +- > 2 files changed, 79 insertions(+), 6 deletions(-) > > diff --git a/kernel/seccomp.c b/kernel/seccomp.c > index 111a238bc532..9921f6f39d12 100644 > --- a/kernel/seccomp.c > +++ b/kernel/seccomp.c > @@ -610,7 +610,12 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog) > { > struct seccomp_filter *sfilter; > int ret; > - const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE); > + const bool save_orig = > +#if defined(CONFIG_CHECKPOINT_RESTORE) || defined(SECCOMP_ARCH) > + true; > +#else > + false; > +#endif You could probably write this as something like: const bool save_orig = IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) || __is_defined(SECCOMP_ARCH); [...] > diff --git a/net/core/filter.c b/net/core/filter.c [...] > -static void bpf_release_orig_filter(struct bpf_prog *fp) > +void bpf_release_orig_filter(struct bpf_prog *fp) > { > struct sock_fprog_kern *fprog = fp->orig_prog; > > @@ -1154,6 +1154,7 @@ static void bpf_release_orig_filter(struct bpf_prog *fp) > kfree(fprog); > } > } > +EXPORT_SYMBOL_GPL(bpf_release_orig_filter); If this change really belongs into this patch (which I don't think it does), please describe why in the commit message.
