[PATCH bpf 5/9] bpf: fix missing error return in check_stack_boundary()

[Alexei Starovoitov]

From: Jann Horn <ja...@google.com>

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 <ja...@google.com>
Signed-off-by: Alexei Starovoitov <a...@kernel.org>
---
 kernel/bpf/verifier.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ecdc265244ca..77e4b5223867 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1303,6 +1303,7 @@ 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 ||
-- 
2.9.5