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authorDaniel Borkmann <daniel@iogearbox.net>2019-01-03 00:58:30 +0100
committerAlexei Starovoitov <ast@kernel.org>2019-01-02 16:01:24 -0800
commit0d6303db7970e6f56ae700fa07e11eb510cda125 (patch)
tree6b9b3ae39535460fef0d17fdb103279ddc726be3 /kernel/bpf
parent9b73bfdd08e73231d6a90ae6db4b46b3fbf56c30 (diff)
bpf: restrict map value pointer arithmetic for unprivileged
Restrict map value pointer arithmetic for unprivileged users in that arithmetic itself must not go out of bounds as opposed to the actual access later on. Therefore after each adjust_ptr_min_max_vals() with a map value pointer as a destination it will simulate a check_map_access() of 1 byte on the destination and once that fails the program is rejected for unprivileged program loads. We use this later on for masking any pointer arithmetic with the remainder of the map value space. The likelihood of breaking any existing real-world unprivileged eBPF program is very small for this corner case. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/verifier.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index afa8515bbb34..4da8c73e168f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3249,6 +3249,17 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
__update_reg_bounds(dst_reg);
__reg_deduce_bounds(dst_reg);
__reg_bound_offset(dst_reg);
+
+ /* For unprivileged we require that resulting offset must be in bounds
+ * in order to be able to sanitize access later on.
+ */
+ if (!env->allow_ptr_leaks && dst_reg->type == PTR_TO_MAP_VALUE &&
+ check_map_access(env, dst, dst_reg->off, 1, false)) {
+ verbose(env, "R%d pointer arithmetic of map value goes out of range, prohibited for !root\n",
+ dst);
+ return -EACCES;
+ }
+
return 0;
}