| Message ID | 20231219134800.1550388-1-menglong8.dong@gmail.com |
|---|---|
| Headers | show |
| Series | bpf: support to track BPF_JNE | expand |
Hello: This series was applied to bpf/bpf-next.git (master) by Alexei Starovoitov <ast@kernel.org>: On Tue, 19 Dec 2023 21:47:56 +0800 you wrote: > For now, the reg bounds is not handled for BPF_JNE case, which can cause > the failure of following case: > > /* The type of "a" is u32 */ > if (a > 0 && a < 100) { > /* the range of the register for a is [0, 99], not [1, 99], > * and will cause the following error: > * > * invalid zero-sized read > * > * as a can be 0. > */ > bpf_skb_store_bytes(skb, xx, xx, a, 0); > } > > [...] Here is the summary with links: - [bpf-next,v5,1/4] bpf: make the verifier tracks the "not equal" for regs https://git.kernel.org/bpf/bpf-next/c/d028f87517d6 - [bpf-next,v5,2/4] selftests/bpf: remove reduplicated s32 casting in "crafted_cases" https://git.kernel.org/bpf/bpf-next/c/1de584832375 - [bpf-next,v5,3/4] selftests/bpf: activate the OP_NE logic in range_cond() https://git.kernel.org/bpf/bpf-next/c/31d9cc96b1e3 - [bpf-next,v5,4/4] selftests/bpf: add testcase to verifier_bounds.c for BPF_JNE https://git.kernel.org/bpf/bpf-next/c/463ea64eb008 You are awesome, thank you!
For now, the reg bounds is not handled for BPF_JNE case, which can cause the failure of following case: /* The type of "a" is u32 */ if (a > 0 && a < 100) { /* the range of the register for a is [0, 99], not [1, 99], * and will cause the following error: * * invalid zero-sized read * * as a can be 0. */ bpf_skb_store_bytes(skb, xx, xx, a, 0); } In the code above, "a > 0" will be compiled to "if a == 0 goto xxx". In the TRUE branch, the dst_reg will be marked as known to 0. However, in the fallthrough(FALSE) branch, the dst_reg will not be handled, which makes the [min, max] for a is [0, 99], not [1, 99]. In the 1st patch, we reduce the range of the dst reg if the src reg is a const and is exactly the edge of the dst reg For BPF_JNE. In the 2nd patch, we remove reduplicated s32 casting in "crafted_cases". In the 3rd patch, we just activate the test case for this logic in range_cond(), which is committed by Andrii in the commit 8863238993e2 ("selftests/bpf: BPF register range bounds tester"). In the 4th patch, we convert the case above to a testcase and add it to verifier_bounds.c. Changes since v4: - add the 2nd patch - add "{U32, U32, {0, U32_MAX}, {U32_MAX, U32_MAX}}" that we missed in the 3rd patch - add some comments to the function that we add in the 4th patch - add reg_not_equal_const() in the 4th patch Changes since v3: - do some adjustment to the crafted cases that we added in the 2nd patch - add the 3rd patch Changes since v2: - fix a typo in the subject of the 1st patch - add some comments to the 1st patch, as Eduard advised - add some cases to the "crafted_cases" Changes since v1: - simplify the code in the 1st patch - introduce the 2nd patch for the testing Menglong Dong (4): bpf: make the verifier tracks the "not equal" for regs selftests/bpf: remove reduplicated s32 casting in "crafted_cases" selftests/bpf: activate the OP_NE logic in range_cond() selftests/bpf: add testcase to verifier_bounds.c for BPF_JNE kernel/bpf/verifier.c | 38 +++++++++++- .../selftests/bpf/prog_tests/reg_bounds.c | 27 +++++--- .../selftests/bpf/progs/verifier_bounds.c | 62 +++++++++++++++++++ 3 files changed, 116 insertions(+), 11 deletions(-)