Commit 257af63d authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann

bpf: Fix modifier skipping logic

Fix the way modifiers are skipped while walking pointers. Otherwise second
level dereferences of 'const struct foo *' will be rejected by the verifier.

Fixes: 9e15db66 ("bpf: Implement accurate raw_tp context access via BTF")
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200201000314.261392-1-ast@kernel.org
parent a525b088
...@@ -3931,6 +3931,7 @@ int btf_struct_access(struct bpf_verifier_log *log, ...@@ -3931,6 +3931,7 @@ int btf_struct_access(struct bpf_verifier_log *log,
if (btf_type_is_ptr(mtype)) { if (btf_type_is_ptr(mtype)) {
const struct btf_type *stype; const struct btf_type *stype;
u32 id;
if (msize != size || off != moff) { if (msize != size || off != moff) {
bpf_log(log, bpf_log(log,
...@@ -3939,12 +3940,9 @@ int btf_struct_access(struct bpf_verifier_log *log, ...@@ -3939,12 +3940,9 @@ int btf_struct_access(struct bpf_verifier_log *log,
return -EACCES; return -EACCES;
} }
stype = btf_type_by_id(btf_vmlinux, mtype->type); stype = btf_type_skip_modifiers(btf_vmlinux, mtype->type, &id);
/* skip modifiers */
while (btf_type_is_modifier(stype))
stype = btf_type_by_id(btf_vmlinux, stype->type);
if (btf_type_is_struct(stype)) { if (btf_type_is_struct(stype)) {
*next_btf_id = mtype->type; *next_btf_id = id;
return PTR_TO_BTF_ID; return PTR_TO_BTF_ID;
} }
} }
......
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