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| author | Jiong Wang <jiong.wang@netronome.com> | 2018-12-15 03:34:40 -0500 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2018-12-18 14:45:01 -0800 |
| commit | 0bae2d4d62d523f06ff1a8e88ce38b45400acd28 (patch) | |
| tree | bf6f6180c0843475a553345c96f4e4c00c2272ca /kernel | |
| parent | a38d1107f937ca95dcf820161ef44ea683d6a0b1 (diff) | |
| download | talos-obmc-linux-0bae2d4d62d523f06ff1a8e88ce38b45400acd28.tar.gz talos-obmc-linux-0bae2d4d62d523f06ff1a8e88ce38b45400acd28.zip | |
bpf: correct slot_type marking logic to allow more stack slot sharing
Verifier is supposed to support sharing stack slot allocated to ptr with
SCALAR_VALUE for privileged program. However this doesn't happen for some
cases.
The reason is verifier is not clearing slot_type STACK_SPILL for all bytes,
it only clears part of them, while verifier is using:
slot_type[0] == STACK_SPILL
as a convention to check one slot is ptr type.
So, the consequence of partial clearing slot_type is verifier could treat a
partially overridden ptr slot, which should now be a SCALAR_VALUE slot,
still as ptr slot, and rejects some valid programs.
Before this patch, test_xdp_noinline.o under bpf selftests, bpf_lxc.o and
bpf_netdev.o under Cilium bpf repo, when built with -mattr=+alu32 are
rejected due to this issue. After this patch, they all accepted.
There is no processed insn number change before and after this patch on
Cilium bpf programs.
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 0125731e2512..e0e77ffeefb8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1286,6 +1286,10 @@ static int check_stack_write(struct bpf_verifier_env *env, /* regular write of data into stack destroys any spilled ptr */ state->stack[spi].spilled_ptr.type = NOT_INIT; + /* Mark slots as STACK_MISC if they belonged to spilled ptr. */ + if (state->stack[spi].slot_type[0] == STACK_SPILL) + for (i = 0; i < BPF_REG_SIZE; i++) + state->stack[spi].slot_type[i] = STACK_MISC; /* only mark the slot as written if all 8 bytes were written * otherwise read propagation may incorrectly stop too soon @@ -1303,6 +1307,7 @@ static int check_stack_write(struct bpf_verifier_env *env, register_is_null(&cur->regs[value_regno])) type = STACK_ZERO; + /* Mark slots affected by this stack write. */ for (i = 0; i < size; i++) state->stack[spi].slot_type[(slot - i) % BPF_REG_SIZE] = type; |
