| Message ID | 20200201000314.261392-1-ast@kernel.org |
|---|---|
| State | Accepted |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf] bpf: Fix modifier skipping logic | expand |
On 1/31/20 4:03 PM, Alexei Starovoitov wrote: > Fix the way modifiers are skipped while walking pointers. Otherwise second > level dereferences of 'const struct foo *' will be rejected by the verifier. > > Fixes: 9e15db66136a ("bpf: Implement accurate raw_tp context access via BTF") > Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Yonghong Song <yhs@fb.com>
On 2/1/20 1:03 AM, Alexei Starovoitov wrote: > Fix the way modifiers are skipped while walking pointers. Otherwise second > level dereferences of 'const struct foo *' will be rejected by the verifier. > > Fixes: 9e15db66136a ("bpf: Implement accurate raw_tp context access via BTF") > Signed-off-by: Alexei Starovoitov <ast@kernel.org> Applied, thanks!
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index b7c1660fb594..a289f2915ba8 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3931,6 +3931,7 @@ int btf_struct_access(struct bpf_verifier_log *log, if (btf_type_is_ptr(mtype)) { const struct btf_type *stype; + u32 id; if (msize != size || off != moff) { bpf_log(log, @@ -3939,12 +3940,9 @@ int btf_struct_access(struct bpf_verifier_log *log, return -EACCES; } - stype = btf_type_by_id(btf_vmlinux, mtype->type); - /* skip modifiers */ - while (btf_type_is_modifier(stype)) - stype = btf_type_by_id(btf_vmlinux, stype->type); + stype = btf_type_skip_modifiers(btf_vmlinux, mtype->type, &id); if (btf_type_is_struct(stype)) { - *next_btf_id = mtype->type; + *next_btf_id = id; return PTR_TO_BTF_ID; } }
Fix the way modifiers are skipped while walking pointers. Otherwise second level dereferences of 'const struct foo *' will be rejected by the verifier. Fixes: 9e15db66136a ("bpf: Implement accurate raw_tp context access via BTF") Signed-off-by: Alexei Starovoitov <ast@kernel.org> --- kernel/bpf/btf.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)