From: Jann Horn <jannh@google.com>
Date: Tue, 19 Dec 2017 04:11:57 +0000 (-0800)
Subject: bpf: fix missing error return in check_stack_boundary()
X-Git-Tag: archive/raspbian/4.15.4-1+rpi1~1^2^2~23
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=b051d0a5bca367dbafe5edf8e3aab9c9c9ce59ae;p=linux.git

bpf: fix missing error return in check_stack_boundary()

Prevent indirect stack accesses at non-constant addresses, which would
permit reading and corrupting spilled pointers.

Fixes: f1174f77b50c ("bpf/verifier: rework value tracking")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name bpf-fix-missing-error-return-in-check_stack_boundary.patch
---

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e6d15c0cf3b..a9f9a5e57ba 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1320,6 +1320,7 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
 		tnum_strn(tn_buf, sizeof(tn_buf), regs[regno].var_off);
 		verbose(env, "invalid variable stack read R%d var_off=%s\n",
 			regno, tn_buf);
+		return -EACCES;
 	}
 	off = regs[regno].off + regs[regno].var_off.value;
 	if (off >= 0 || off < -MAX_BPF_STACK || off + access_size > 0 ||