netdev - [PATCH] bpf: fix missing checks of the return value of check_reg

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Date:   Tue, 25 Dec 2018 01:17:10 -0600
From:   Kangjie Lu <kjlu@....edu>
To:     kjlu@....edu
Cc:     pakki001@....edu, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] bpf: fix missing checks of the return value of check_reg_arg

check_reg_arg() may fail. This fix inserts checks for its return value.
If check_reg_arg() fails, issues an error message.

Signed-off-by: Kangjie Lu <kjlu@....edu>
---
 kernel/bpf/verifier.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 51ba84d4d34a..fde91a5c0b5a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2619,7 +2619,10 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	/* after the call registers r0 - r5 were scratched */
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		mark_reg_not_init(env, caller->regs, caller_saved[i]);
-		check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+		err = check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+		if (err)
+			verbose(env,
+					"check_reg_arg() fails in setting caller saved regs\n");
 	}
 
 	/* only increment it after check_reg_arg() finished */
@@ -2842,7 +2845,10 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
 	/* reset caller saved regs */
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		mark_reg_not_init(env, regs, caller_saved[i]);
-		check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+		err = check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+		if (err)
+			verbose(env,
+				"check_reg_arg() fails in resetting caller saved regs\n");
 	}
 
 	/* update return register (already marked as written above) */
@@ -4435,7 +4441,10 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	/* reset caller saved regs to unreadable */
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		mark_reg_not_init(env, regs, caller_saved[i]);
-		check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+		err = check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+		if (err)
+			verbose(env,
+				"check_reg_arg() fails in resetting caller saved regs to unreadable\n");
 	}
 
 	/* mark destination R0 register as readable, since it contains
-- 
2.17.2 (Apple Git-113)