[PATCH 4.18 03/34] bpf: fix partial copy of map_ptr when dst is scalar

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

commit 0962590e553331db2cc0aef2dc35c57f6300dbbe upstream.

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 <dan...@iogearbox.net>
Cc: Edward Cree <ec...@solarflare.com>
Acked-by: Alexei Starovoitov <a...@kernel.org>
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
Acked-by: Edward Cree <ec...@solarflare.com>
Signed-off-by: Sasha Levin <sas...@kernel.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 38b04f559ad3..1fd6fa822d2c 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -50,6 +50,9 @@ 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 82e8edef6ea0..b000686fa1a1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2731,7 +2731,7 @@ 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
@@ -2761,10 +2761,11 @@ 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:
@@ -2793,7 +2794,7 @@ 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
@@ -2819,11 +2820,12 @@ 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:
-- 
2.17.1