Merge drm/drm-next into drm-misc-next

Backmerging to get drm-misc-next up to v7.3-rc2. Requested for
commit 3a2c4d55e32a ("treewide: refresh kmalloc_obj() conversions").

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

1 files changed, 36 insertions, 26 deletions

diff --git a/kernel/bpf/backtrack.c b/kernel/bpf/backtrack.c
index a2b18a9f1694..47282ffeeaf9 100644
--- a/kernel/bpf/backtrack.c
+++ b/kernel/bpf/backtrack.c
@@ -520,37 +520,34 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
 					return -EFAULT;
 			}
 		} else if (opcode == BPF_EXIT) {
-			bool r0_precise;
+			bool from_subprog_call, r0_precise;
+
+			/* BPF_EXIT in subprog or callback always returns
+			 * right after the call instruction, so by checking
+			 * whether the instruction at subseq_idx-1 is subprog
+			 * call or not we can distinguish actual exit from
+			 * *subprog* from exit from *callback*. In the former
+			 * case, we need to propagate r0 precision, if
+			 * necessary. In the former we never do that.
+			 */
+			from_subprog_call = subseq_idx - 1 >= 0 &&
+					    bpf_pseudo_call(&env->prog->insnsi[subseq_idx - 1]);
+
+			r0_precise = from_subprog_call && bt_is_reg_set(bt, BPF_REG_0);
 
 			/* Backtracking to a nested function call, 'idx' is a part of
 			 * the inner frame 'subseq_idx' is a part of the outer frame.
 			 * In case of a regular function call, instructions giving
 			 * precision to registers R1-R5 should have been found already.
-			 * In case of a callback, it is ok to have R1-R5 marked for
-			 * backtracking, as these registers are set by the function
-			 * invoking callback.
+			 * In case of a callback from bpf_loop(), R{1,4} in the calling
+			 * frame would be set as precise and that is correct.
 			 */
-			if (subseq_idx >= 0 && bpf_calls_callback(env, subseq_idx))
-				for (i = BPF_REG_1; i <= BPF_REG_5; i++)
-					bt_clear_reg(bt, i);
-			if (bt_reg_mask(bt) & BPF_REGMASK_ARGS) {
+			if (from_subprog_call && (bt_reg_mask(bt) & BPF_REGMASK_ARGS)) {
 				verifier_bug(env, "backtracking exit unexpected regs %x",
 					     bt_reg_mask(bt));
 				return -EFAULT;
 			}
 
-			/* BPF_EXIT in subprog or callback always returns
-			 * right after the call instruction, so by checking
-			 * whether the instruction at subseq_idx-1 is subprog
-			 * call or not we can distinguish actual exit from
-			 * *subprog* from exit from *callback*. In the former
-			 * case, we need to propagate r0 precision, if
-			 * necessary. In the former we never do that.
-			 */
-			r0_precise = subseq_idx - 1 >= 0 &&
-				     bpf_pseudo_call(&env->prog->insnsi[subseq_idx - 1]) &&
-				     bt_is_reg_set(bt, BPF_REG_0);
-
 			bt_clear_reg(bt, BPF_REG_0);
 			if (bt_subprog_enter(bt))
 				return -EFAULT;
@@ -582,16 +579,29 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx, int subseq_idx,
 			  */
 		}
 	} else if (class == BPF_LD) {
-		if (!bt_is_reg_set(bt, dreg))
-			return 0;
-		bt_clear_reg(bt, dreg);
 		/* It's ld_imm64 or ld_abs or ld_ind.
 		 * For ld_imm64 no further tracking of precision
 		 * into parent is necessary
 		 */
-		if (mode == BPF_IND || mode == BPF_ABS)
-			/* to be analyzed */
-			return -ENOTSUPP;
+		if (mode == BPF_IMM) {
+			bt_clear_reg(bt, dreg);
+			return 0;
+		}
+		/*
+		 * BPF_{IND,ABS} are modelled as two branches:
+		 * - fallthrough;
+		 * - implicit subprogram exit.
+		 * It is necessary to switch current frame if
+		 * implicit subprogram exit branch is backtracked.
+		 */
+		if (mode == BPF_IND || mode == BPF_ABS) {
+			if (bt_is_reg_set(bt, dreg))
+				return -ENOTSUPP;
+			if (subseq_idx != idx + 1)
+				if (bt_subprog_enter(bt))
+					return -EFAULT;
+			return 0;
+		}
 	}
 	/* Propagate precision marks to linked registers, to account for
 	 * registers marked as precise in this function.