netdev - [PATCH bpf 1/4] bpf: fix partial copy of map

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Message-Id: <20181031230555.3371-2-daniel@iogearbox.net>
Date:   Thu,  1 Nov 2018 00:05:52 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     ast@...nel.org
Cc:     netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
        Edward Cree <ecree@...arflare.com>
Subject: [PATCH bpf 1/4] bpf: fix partial copy of map_ptr when dst is scalar

ALU operations on pointers such as scalar_reg += map_value_ptr are
handled in adjust_ptr_min_max_vals(). Problem is however that map_ptr
and range in the register state share a union, so transferring state
through dst_reg->range = ptr_reg->range is just buggy as any new
map_ptr in the dst_reg is then truncated (or null) for subsequent
checks. Fix this by adding a raw member and use it for copying state
over to dst_reg.

Fixes: f1174f77b50c ("bpf/verifier: rework value tracking")
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Cc: Edward Cree <ecree@...arflare.com>
Acked-by: Alexei Starovoitov <ast@...nel.org>
---
 include/linux/bpf_verifier.h |  3 +++
 kernel/bpf/verifier.c        | 10 ++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 9e8056e..d93e897 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -51,6 +51,9 @@ struct bpf_reg_state {
 		 *   PTR_TO_MAP_VALUE_OR_NULL
 		 */
 		struct bpf_map *map_ptr;
+
+		/* Max size from any of the above. */
+		unsigned long raw;
 	};
 	/* Fixed part of pointer offset, pointer types only */
 	s32 off;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 171a2c8..774fa40 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3046,7 +3046,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 			dst_reg->umax_value = umax_ptr;
 			dst_reg->var_off = ptr_reg->var_off;
 			dst_reg->off = ptr_reg->off + smin_val;
-			dst_reg->range = ptr_reg->range;
+			dst_reg->raw = ptr_reg->raw;
 			break;
 		}
 		/* A new variable offset is created.  Note that off_reg->off
@@ -3076,10 +3076,11 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		}
 		dst_reg->var_off = tnum_add(ptr_reg->var_off, off_reg->var_off);
 		dst_reg->off = ptr_reg->off;
+		dst_reg->raw = ptr_reg->raw;
 		if (reg_is_pkt_pointer(ptr_reg)) {
 			dst_reg->id = ++env->id_gen;
 			/* something was added to pkt_ptr, set range to zero */
-			dst_reg->range = 0;
+			dst_reg->raw = 0;
 		}
 		break;
 	case BPF_SUB:
@@ -3108,7 +3109,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 			dst_reg->var_off = ptr_reg->var_off;
 			dst_reg->id = ptr_reg->id;
 			dst_reg->off = ptr_reg->off - smin_val;
-			dst_reg->range = ptr_reg->range;
+			dst_reg->raw = ptr_reg->raw;
 			break;
 		}
 		/* A new variable offset is created.  If the subtrahend is known
@@ -3134,11 +3135,12 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		}
 		dst_reg->var_off = tnum_sub(ptr_reg->var_off, off_reg->var_off);
 		dst_reg->off = ptr_reg->off;
+		dst_reg->raw = ptr_reg->raw;
 		if (reg_is_pkt_pointer(ptr_reg)) {
 			dst_reg->id = ++env->id_gen;
 			/* something was added to pkt_ptr, set range to zero */
 			if (smin_val < 0)
-				dst_reg->range = 0;
+				dst_reg->raw = 0;
 		}
 		break;
 	case BPF_AND:
-- 
2.9.5