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From: "Toke Høiland-Jørgensen" <>
To: Andrii Nakryiko <>
Cc: Andrii Nakryiko <>, bpf <>,
	Networking <>
Subject: Re: [PATCH bpf] libbpf: don't crash on object files with no symbol tables
Date: Wed, 01 Sep 2021 12:19:10 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Andrii Nakryiko <> writes:

> On Tue, Aug 31, 2021 at 9:58 AM Toke Høiland-Jørgensen <> wrote:
>> 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. Add a check and return to avoid
>> this.
>> Fixes: 6245947c1b3c ("libbpf: Allow gaps in BPF program sections to support overriden weak functions")
>> Signed-off-by: Toke Høiland-Jørgensen <>
>> ---
>>  tools/lib/bpf/libbpf.c | 3 +++
>>  1 file changed, 3 insertions(+)
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 6f5e2757bb3c..4cd102affeef 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -668,6 +668,9 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data,
>>         const char *name;
>>         GElf_Sym sym;
>> +       if (!symbols)
>> +               return -ENOENT;
>> +
> The more logical place to do this check is in
> bpf_object__elf_collect(). Can you add this there? We can also include
> helpful error message.

Sure, can do.

> But I'm also curious which Clang version is being used to cause no ELF
> symbols being generated?

It's not Clang. I was debugging an issue with 'strip' mangling BPF
object files and ran into this after trying to load an object file that
had been run through a full 'strip bpf_object.o' (whereas 'strip -g
bpf_object.o' works fine, except for that one bug I'm looking at).


      reply	other threads:[~2021-09-01 10:19 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-31 16:58 [PATCH bpf] libbpf: don't crash on object files with no symbol tables Toke Høiland-Jørgensen
2021-08-31 22:45 ` Andrii Nakryiko
2021-09-01 10:19   ` Toke Høiland-Jørgensen [this message]

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