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[v2,bpf-next,07/11] libbpf: fix BTF data layout checks and allow empty BTF

Message ID 20201105043402.2530976-8-andrii@kernel.org
State Not Applicable
Delegated to: BPF Maintainers
Headers show
Series libbpf: split BTF support | expand


Context Check Description
jkicinski/cover_letter success Link
jkicinski/fixes_present success Link
jkicinski/patch_count success Link
jkicinski/tree_selection success Clearly marked for bpf-next
jkicinski/subject_prefix success Link
jkicinski/source_inline success Was 0 now: 0
jkicinski/verify_signedoff success Link
jkicinski/module_param success Was 0 now: 0
jkicinski/build_32bit fail Errors and warnings before: 4 this patch: 4
jkicinski/kdoc success Errors and warnings before: 0 this patch: 0
jkicinski/verify_fixes success Link
jkicinski/checkpatch fail Link
jkicinski/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
jkicinski/header_inline success Link
jkicinski/stable success Stable not CCed

Commit Message

Andrii Nakryiko Nov. 5, 2020, 4:33 a.m. UTC
Make data section layout checks stricter, disallowing overlap of types and
strings data.

Additionally, allow BTFs with no type data. There is nothing inherently wrong
with having BTF with no types (put potentially with some strings). This could
be a situation with kernel module BTFs, if module doesn't introduce any new
type information.

Also fix invalid offset alignment check for btf->hdr->type_off.

Fixes: 8a138aed4a80 ("bpf: btf: Add BTF support to libbpf")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
 tools/lib/bpf/btf.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)
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diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 0258cf108c0a..20bb88e71f07 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -245,22 +245,18 @@  static int btf_parse_hdr(struct btf *btf)
 		return -EINVAL;
-	if (meta_left < hdr->type_off) {
-		pr_debug("Invalid BTF type section offset:%u\n", hdr->type_off);
+	if (meta_left < hdr->str_off + hdr->str_len) {
+		pr_debug("Invalid BTF total size:%u\n", btf->raw_size);
 		return -EINVAL;
-	if (meta_left < hdr->str_off) {
-		pr_debug("Invalid BTF string section offset:%u\n", hdr->str_off);
+	if (hdr->type_off + hdr->type_len > hdr->str_off) {
+		pr_debug("Invalid BTF data sections layout: type data at %u + %u, strings data at %u + %u\n",
+			 hdr->type_off, hdr->type_len, hdr->str_off, hdr->str_len);
 		return -EINVAL;
-	if (hdr->type_off >= hdr->str_off) {
-		pr_debug("BTF type section offset >= string section offset. No type?\n");
-		return -EINVAL;
-	}
-	if (hdr->type_off & 0x02) {
+	if (hdr->type_off % 4) {
 		pr_debug("BTF type section is not aligned to 4 bytes\n");
 		return -EINVAL;