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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: f1174f77b5 ("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>
This commit is contained in:
Jann Horn 2017-12-18 20:11:57 -08:00 committed by Daniel Borkmann
parent 468f6eafa6
commit ea25f914dc
1 changed files with 1 additions and 0 deletions
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kernel/bpf/verifier.c
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@ -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 ||