[PATCH 5.15 330/917] libbpf: Dont crash on object files with no symbol tables

Greg Kroah-Hartman
2021-11-15T23:36:25Z

From: Toke Høiland-Jørgensen <toke@redhat.com>

[ Upstream commit 03e601f48b2da6fb44d0f7b86957a8f6bacfb347 ]

If libbpf encounters an ELF file that has been stripped of its symbol
table, it will crash in bpf_object__add_programs() when trying to
dereference the obj->efile.symbols pointer.

Fix this by erroring out of bpf_object__elf_collect() if it is not able
able to find the symbol table.

v2:
- Move check into bpf_object__elf_collect() and add nice error message

Fixes: 6245947c1b3c ("libbpf: Allow gaps in BPF program sections to support overriden weak functions")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210901114812.204720-1-toke@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/bpf/libbpf.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e4f83c304ec92..51180f300d2e1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2993,6 +2993,12 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
}
}

+ if (!obj->efile.symbols) {
+ pr_warn("elf: couldn't find symbol table in %s, stripped object file?\n",
+ obj->path);
+ return -ENOENT;
+ }
+
scn = NULL;
while ((scn = elf_nextscn(elf, scn)) != NULL) {
idx++;
--
2.33.0