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authorJiong Wang <jiong.wang@netronome.com>2018-12-15 03:34:40 -0500
committerAlexei Starovoitov <ast@kernel.org>2018-12-18 14:45:01 -0800
commit0bae2d4d62d523f06ff1a8e88ce38b45400acd28 (patch)
treebf6f6180c0843475a553345c96f4e4c00c2272ca /kernel
parenta38d1107f937ca95dcf820161ef44ea683d6a0b1 (diff)
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.c5
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;