On Thu, Nov 3, 2022 at 1:36 AM Yang Jihong yangjihong1@huawei.com wrote:
The error code -EACCES is returned when bpf prog is tested in 32-bit environment, This is because bpf_object__relocate modifies the instruction to change memory size to 4 bytes, as shown in the following messages:
libbpf: prog 'kfunc_call_test1': relo #2: matching candidate #0 <byte_off> [18342] struct __sk_buff.sk (0:30:0 @ offset 168) libbpf: prog 'kfunc_call_test1': relo #2: patched insn #1 (LDX/ST/STX) off 168 -> 168 libbpf: prog 'kfunc_call_test1': relo #2: patched insn #1 (LDX/ST/STX) mem_sz 8 -> 4
As a result, the bpf_skb_is_valid_access check fails. For 32-bit architecture, unnecessary checks need to be deleted.
Signed-off-by: Yang Jihong yangjihong1@huawei.com
net/core/filter.c | 2 -- 1 file changed, 2 deletions(-)
diff --git a/net/core/filter.c b/net/core/filter.c index bb0136e7a8e4..eab7ce89740c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8269,8 +8269,6 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type return false; break; case offsetof(struct __sk_buff, sk):
if (type == BPF_WRITE || size != sizeof(__u64))return false;
this probably should be specific to host architecture bitness? I'd imagine that size = 4 should be invalid on 64-bit arches (reading half of the pointer is bad)
either way, please make sure to add tests specifically for this case in test_verifier
info->reg_type = PTR_TO_SOCK_COMMON_OR_NULL; break; case offsetof(struct __sk_buff, tstamp_type):-- 2.30.GIT