From: Daniel Borkmann daniel@iogearbox.net
[ Upstream commit e60b0d12a95dcf16a63225cead4541567f5cb517 ]
If we ever get to a point again where we convert a bogus looking <ptr>_or_null typed register containing a non-zero fixed or variable offset, then lets not reset these bounds to zero since they are not and also don't promote the register to a <ptr> type, but instead leave it as <ptr>_or_null. Converting to a unknown register could be an avenue as well, but then if we run into this case it would allow to leak a kernel pointer this way.
Fixes: f1174f77b50c ("bpf/verifier: rework value tracking") Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/verifier.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c623c3e549210..015bf2ba4a0b6 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -7725,15 +7725,15 @@ static void mark_ptr_or_null_reg(struct bpf_func_state *state, { if (reg_type_may_be_null(reg->type) && reg->id == id && !WARN_ON_ONCE(!reg->id)) { - /* Old offset (both fixed and variable parts) should - * have been known-zero, because we don't allow pointer - * arithmetic on pointers that might be NULL. - */ if (WARN_ON_ONCE(reg->smin_value || reg->smax_value || !tnum_equals_const(reg->var_off, 0) || reg->off)) { - __mark_reg_known_zero(reg); - reg->off = 0; + /* Old offset (both fixed and variable parts) should + * have been known-zero, because we don't allow pointer + * arithmetic on pointers that might be NULL. If we + * see this happening, don't convert the register. + */ + return; } if (is_null) { reg->type = SCALAR_VALUE;