bpf/verifier: rework value tracking

Unifies adjusted and unadjusted register value types (e.g. FRAME_POINTER is
 now just a PTR_TO_STACK with zero offset).
Tracks value alignment by means of tracking known & unknown bits.  This
 also replaces the 'reg->imm' (leading zero bits) calculations for (what
 were) UNKNOWN_VALUEs.
If pointer leaks are allowed, and adjust_ptr_min_max_vals returns -EACCES,
 treat the pointer as an unknown scalar and try again, because we might be
 able to conclude something about the result (e.g. pointer & 0x40 is either
 0 or 0x40).
Verifier hooks in the netronome/nfp driver were changed to match the new
 data structures.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 22 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 6353c7474dba..39229c455cba 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -117,35 +117,25 @@ enum bpf_access_type {
 };
 
 /* types of values stored in eBPF registers */
+/* Pointer types represent:
+ * pointer
+ * pointer + imm
+ * pointer + (u16) var
+ * pointer + (u16) var + imm
+ * if (range > 0) then [ptr, ptr + range - off) is safe to access
+ * if (id > 0) means that some 'var' was added
+ * if (off > 0) means that 'imm' was added
+ */
 enum bpf_reg_type {
 	NOT_INIT = 0,		 /* nothing was written into register */
-	UNKNOWN_VALUE,		 /* reg doesn't contain a valid pointer */
+	SCALAR_VALUE,		 /* reg doesn't contain a valid pointer */
 	PTR_TO_CTX,		 /* reg points to bpf_context */
 	CONST_PTR_TO_MAP,	 /* reg points to struct bpf_map */
 	PTR_TO_MAP_VALUE,	 /* reg points to map element value */
 	PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */
-	FRAME_PTR,		 /* reg == frame_pointer */
-	PTR_TO_STACK,		 /* reg == frame_pointer + imm */
-	CONST_IMM,		 /* constant integer value */
-
-	/* PTR_TO_PACKET represents:
-	 * skb->data
-	 * skb->data + imm
-	 * skb->data + (u16) var
-	 * skb->data + (u16) var + imm
-	 * if (range > 0) then [ptr, ptr + range - off) is safe to access
-	 * if (id > 0) means that some 'var' was added
-	 * if (off > 0) menas that 'imm' was added
-	 */
-	PTR_TO_PACKET,
+	PTR_TO_STACK,		 /* reg == frame_pointer + offset */
+	PTR_TO_PACKET,		 /* reg points to skb->data */
 	PTR_TO_PACKET_END,	 /* skb->data + headlen */
-
-	/* PTR_TO_MAP_VALUE_ADJ is used for doing pointer math inside of a map
-	 * elem value.  We only allow this if we can statically verify that
-	 * access from this register are going to fall within the size of the
-	 * map element.
-	 */
-	PTR_TO_MAP_VALUE_ADJ,
 };
 
 struct bpf_prog;