From b5ed021bbc47efe77732b38b5946116be94367e1 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Fri, 13 Apr 2018 14:02:24 +0200 Subject: [PATCH] seccomp: handle arch inversion This commit deals with different kernel and userspace layouts and nesting. Here are three examples: 1. 64bit kernel and 64bit userspace running 32bit containers 2. 64bit kernel and 32bit userspace running 64bit containers 3. 64bit kernel and 64bit userspace running 32bit containers running 64bit containers Two things to lookout for: 1. The compat arch that is detected might have already been present in the main context. So check that it actually hasn't been and only then add it. 2. The contexts don't need merging if the architectures are the same and also can't be. With these changes I can run all crazy/weird combinations with proper seccomp isolation. Closes #654. Link: https://bugs.chromium.org/p/chromium/issues/detail?id=832366 Reported-by: Chirantan Ekbote Reported-by: Sonny Rao Signed-off-by: Christian Brauner --- src/lxc/seccomp.c | 48 +++++++++++++++++++++++++++++++---------------- 1 file changed, 32 insertions(+), 16 deletions(-) diff --git a/src/lxc/seccomp.c b/src/lxc/seccomp.c index 310a742fc..5da31a563 100644 --- a/src/lxc/seccomp.c +++ b/src/lxc/seccomp.c @@ -370,17 +370,21 @@ scmp_filter_ctx get_new_ctx(enum lxc_hostarch_t n_arch, uint32_t default_policy_ WARN("Failed to turn on seccomp nop-skip, continuing"); } #endif - ret = seccomp_arch_add(ctx, arch); - if (ret != 0) { - ERROR("Seccomp error %d (%s) adding arch: %d", ret, - strerror(-ret), (int)n_arch); - seccomp_release(ctx); - return NULL; - } - if (seccomp_arch_remove(ctx, SCMP_ARCH_NATIVE) != 0) { - ERROR("Seccomp error removing native arch"); - seccomp_release(ctx); - return NULL; + + if (seccomp_arch_exist(ctx, arch) == -EEXIST) { + ret = seccomp_arch_add(ctx, arch); + if (ret != 0) { + ERROR("Seccomp error %d (%s) adding arch: %d", ret, + strerror(-ret), (int)n_arch); + seccomp_release(ctx); + return NULL; + } + + if (seccomp_arch_remove(ctx, SCMP_ARCH_NATIVE) != 0) { + ERROR("Seccomp error removing native arch"); + seccomp_release(ctx); + return NULL; + } } return ctx; @@ -772,11 +776,23 @@ static int parse_config_v2(FILE *f, char *line, struct lxc_conf *conf) } if (compat_ctx[0]) { - INFO("Merging in the compat Seccomp ctx into the main one"); - if (seccomp_merge(conf->seccomp_ctx, compat_ctx[0]) != 0 || - (compat_ctx[1] != NULL && seccomp_merge(conf->seccomp_ctx, compat_ctx[1]) != 0)) { - ERROR("Error merging compat Seccomp contexts"); - goto bad; + INFO("Merging compat seccomp contexts into main context"); + if (compat_arch[0] != native_arch && compat_arch[0] != seccomp_arch_native()) { + ret = seccomp_merge(conf->seccomp_ctx, compat_ctx[0]); + if (ret < 0) { + ERROR("Failed to merge first compat seccomp context into main context"); + goto bad; + } + TRACE("Merged first compat seccomp context into main context"); + } + + if (compat_arch[1] && compat_arch[1] != native_arch && compat_arch[1] != seccomp_arch_native()) { + ret = seccomp_merge(conf->seccomp_ctx, compat_ctx[1]); + if (ret < 0) { + ERROR("Failed to merge first compat seccomp context into main context"); + goto bad; + } + TRACE("Merged second compat seccomp context into main context"); } }