diff mbox series

[net-next,3/7] bpf: don't mark FP reg as uninit

Message ID 20171201053141.3992592-4-ast@fb.com
State Accepted, archived
Delegated to: BPF Maintainers
Headers show
Series bpf: verifier improvements and cleanups | expand

Commit Message

Alexei Starovoitov Dec. 1, 2017, 5:31 a.m. UTC 
when verifier hits an internal bug don't mark register R10==FP as uninit,
since it's read only register and it's not technically correct to let
verifier run further, since it may assume that R10 has valid auxiliary state.

While developing subsequent patches this issue was discovered,
though the code eventually changed that aux reg state doesn't have
pointers any more it is still safer to avoid clearing readonly register.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
---
 kernel/bpf/verifier.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f7229390c279..14ad7c6e806a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -584,8 +584,8 @@  static void mark_reg_unknown(struct bpf_verifier_env *env,
 {
 	if (WARN_ON(regno >= MAX_BPF_REG)) {
 		verbose(env, "mark_reg_unknown(regs, %u)\n", regno);
-		/* Something bad happened, let's kill all regs */
-		for (regno = 0; regno < MAX_BPF_REG; regno++)
+		/* Something bad happened, let's kill all regs except FP */
+		for (regno = 0; regno < BPF_REG_FP; regno++)
 			__mark_reg_not_init(regs + regno);
 		return;
 	}
@@ -603,8 +603,8 @@  static void mark_reg_not_init(struct bpf_verifier_env *env,
 {
 	if (WARN_ON(regno >= MAX_BPF_REG)) {
 		verbose(env, "mark_reg_not_init(regs, %u)\n", regno);
-		/* Something bad happened, let's kill all regs */
-		for (regno = 0; regno < MAX_BPF_REG; regno++)
+		/* Something bad happened, let's kill all regs except FP */
+		for (regno = 0; regno < BPF_REG_FP; regno++)
 			__mark_reg_not_init(regs + regno);
 		return;
 	}