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Diffstat (limited to 'kernel/seccomp.c')
-rw-r--r--kernel/seccomp.c156
1 files changed, 155 insertions, 1 deletions
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index fe35f4f38949..d8cf468dbe1e 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -169,6 +169,10 @@ static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilte
{
return false;
}
+
+static inline void seccomp_cache_prepare(struct seccomp_filter *sfilter)
+{
+}
#endif /* SECCOMP_ARCH_NATIVE */
/**
@@ -187,6 +191,7 @@ static inline bool seccomp_cache_check_allow(const struct seccomp_filter *sfilte
* this filter after reaching 0. The @users count is always smaller
* or equal to @refs. Hence, reaching 0 for @users does not mean
* the filter can be freed.
+ * @cache: cache of arch/syscall mappings to actions
* @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
* @prev: points to a previously installed, or inherited, filter
* @prog: the BPF program to evaluate
@@ -208,6 +213,7 @@ struct seccomp_filter {
refcount_t refs;
refcount_t users;
bool log;
+ struct action_cache cache;
struct seccomp_filter *prev;
struct bpf_prog *prog;
struct notification *notif;
@@ -621,7 +627,12 @@ 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_NATIVE)
+ true;
+#else
+ false;
+#endif
if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
return ERR_PTR(-EINVAL);
@@ -687,6 +698,148 @@ out:
return filter;
}
+#ifdef SECCOMP_ARCH_NATIVE
+/**
+ * seccomp_is_const_allow - check if filter is constant allow with given data
+ * @fprog: The BPF programs
+ * @sd: The seccomp data to check against, only syscall number and arch
+ * number are considered constant.
+ */
+static bool seccomp_is_const_allow(struct sock_fprog_kern *fprog,
+ struct seccomp_data *sd)
+{
+ unsigned int reg_value = 0;
+ unsigned int pc;
+ bool op_res;
+
+ if (WARN_ON_ONCE(!fprog))
+ return false;
+
+ for (pc = 0; pc < fprog->len; pc++) {
+ struct sock_filter *insn = &fprog->filter[pc];
+ u16 code = insn->code;
+ u32 k = insn->k;
+
+ switch (code) {
+ case BPF_LD | BPF_W | BPF_ABS:
+ switch (k) {
+ case offsetof(struct seccomp_data, nr):
+ reg_value = sd->nr;
+ break;
+ case offsetof(struct seccomp_data, arch):
+ reg_value = sd->arch;
+ break;
+ default:
+ /* can't optimize (non-constant value load) */
+ return false;
+ }
+ break;
+ case BPF_RET | BPF_K:
+ /* reached return with constant values only, check allow */
+ return k == SECCOMP_RET_ALLOW;
+ case BPF_JMP | BPF_JA:
+ pc += insn->k;
+ break;
+ case BPF_JMP | BPF_JEQ | BPF_K:
+ case BPF_JMP | BPF_JGE | BPF_K:
+ case BPF_JMP | BPF_JGT | BPF_K:
+ case BPF_JMP | BPF_JSET | BPF_K:
+ switch (BPF_OP(code)) {
+ case BPF_JEQ:
+ op_res = reg_value == k;
+ break;
+ case BPF_JGE:
+ op_res = reg_value >= k;
+ break;
+ case BPF_JGT:
+ op_res = reg_value > k;
+ break;
+ case BPF_JSET:
+ op_res = !!(reg_value & k);
+ break;
+ default:
+ /* can't optimize (unknown jump) */
+ return false;
+ }
+
+ pc += op_res ? insn->jt : insn->jf;
+ break;
+ case BPF_ALU | BPF_AND | BPF_K:
+ reg_value &= k;
+ break;
+ default:
+ /* can't optimize (unknown insn) */
+ return false;
+ }
+ }
+
+ /* ran off the end of the filter?! */
+ WARN_ON(1);
+ return false;
+}
+
+static void seccomp_cache_prepare_bitmap(struct seccomp_filter *sfilter,
+ void *bitmap, const void *bitmap_prev,
+ size_t bitmap_size, int arch)
+{
+ struct sock_fprog_kern *fprog = sfilter->prog->orig_prog;
+ struct seccomp_data sd;
+ int nr;
+
+ if (bitmap_prev) {
+ /* The new filter must be as restrictive as the last. */
+ bitmap_copy(bitmap, bitmap_prev, bitmap_size);
+ } else {
+ /* Before any filters, all syscalls are always allowed. */
+ bitmap_fill(bitmap, bitmap_size);
+ }
+
+ for (nr = 0; nr < bitmap_size; nr++) {
+ /* No bitmap change: not a cacheable action. */
+ if (!test_bit(nr, bitmap))
+ continue;
+
+ sd.nr = nr;
+ sd.arch = arch;
+
+ /* No bitmap change: continue to always allow. */
+ if (seccomp_is_const_allow(fprog, &sd))
+ continue;
+
+ /*
+ * Not a cacheable action: always run filters.
+ * atomic clear_bit() not needed, filter not visible yet.
+ */
+ __clear_bit(nr, bitmap);
+ }
+}
+
+/**
+ * seccomp_cache_prepare - emulate the filter to find cachable syscalls
+ * @sfilter: The seccomp filter
+ *
+ * Returns 0 if successful or -errno if error occurred.
+ */
+static void seccomp_cache_prepare(struct seccomp_filter *sfilter)
+{
+ struct action_cache *cache = &sfilter->cache;
+ const struct action_cache *cache_prev =
+ sfilter->prev ? &sfilter->prev->cache : NULL;
+
+ seccomp_cache_prepare_bitmap(sfilter, cache->allow_native,
+ cache_prev ? cache_prev->allow_native : NULL,
+ SECCOMP_ARCH_NATIVE_NR,
+ SECCOMP_ARCH_NATIVE);
+
+#ifdef SECCOMP_ARCH_COMPAT
+ seccomp_cache_prepare_bitmap(sfilter, cache->allow_compat,
+ cache_prev ? cache_prev->allow_compat : NULL,
+ SECCOMP_ARCH_COMPAT_NR,
+ SECCOMP_ARCH_COMPAT);
+#endif /* SECCOMP_ARCH_COMPAT */
+}
+#endif /* SECCOMP_ARCH_NATIVE */
+
/**
* seccomp_attach_filter: validate and attach filter
* @flags: flags to change filter behavior
@@ -736,6 +889,7 @@ static long seccomp_attach_filter(unsigned int flags,
* task reference.
*/
filter->prev = current->seccomp.filter;
+ seccomp_cache_prepare(filter);
current->seccomp.filter = filter;
atomic_inc(&current->seccomp.filter_count);