netdev - [PATCH bpf-next] libbpf: fix off-by-one error in ELF sanity check

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Message-ID: <20191028233727.1286699-1-andriin@fb.com>
Date:   Mon, 28 Oct 2019 16:37:27 -0700
From:   Andrii Nakryiko <andriin@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii.nakryiko@...il.com>, <kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf-next] libbpf: fix off-by-one error in ELF sanity check

libbpf's bpf_object__elf_collect() does simple sanity check after iterating
over all ELF sections, if checks that .strtab index is correct. Unfortunately,
due to section indices being 1-based, the check breaks for cases when .strtab
ends up being the very last section in ELF.

Fixes: 77ba9a5b48a7 ("tools lib bpf: Fetch map names from correct strtab")
Signed-off-by: Andrii Nakryiko <andriin@...com>
---
 tools/lib/bpf/libbpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index d71631a01926..5d15cc4dfcd6 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1664,7 +1664,7 @@ static int bpf_object__elf_collect(struct bpf_object *obj, bool relaxed_maps)
 		}
 	}
 
-	if (!obj->efile.strtabidx || obj->efile.strtabidx >= idx) {
+	if (!obj->efile.strtabidx || obj->efile.strtabidx > idx) {
 		pr_warn("Corrupted ELF file: index of strtab invalid\n");
 		return -LIBBPF_ERRNO__FORMAT;
 	}
-- 
2.17.1