linux-kernel - Re: [PATCH bpf-next v3] bpftool: Fix gen object segfault

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Message-ID: <0b96aa24-13ca-4e0a-8e80-f2586fbe2b57@kernel.org>
Date: Thu, 5 Dec 2024 12:22:39 +0000
From: Quentin Monnet <qmo@...nel.org>
To: Rong Tao <rtoax@...mail.com>, ast@...nel.org, daniel@...earbox.net,
 rongtao@...tc.cn
Cc: Andrii Nakryiko <andrii@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>,
 "open list:BPF [TOOLING] (bpftool)" <bpf@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v3] bpftool: Fix gen object segfault

On 05/12/2024 12:09, Rong Tao wrote:
> From: Rong Tao <rongtao@...tc.cn>
> 
> If the input file and output file are the same, the input file is cleared
> due to opening, resulting in a NULL pointer access by libbpf.
> 
>     $ bpftool gen object prog.o prog.o
>     libbpf: failed to get ELF header for prog.o: invalid `Elf' handle
>     Segmentation fault
> 
>     (gdb) bt
>     #0  0x0000000000450285 in linker_append_elf_syms (linker=0x4feda0, obj=0x7fffffffe100) at linker.c:1296
>     #1  bpf_linker__add_file (linker=0x4feda0, filename=<optimized out>, opts=<optimized out>) at linker.c:453
>     #2  0x000000000040c235 in do_object ()
>     #3  0x00000000004021d7 in main ()
>     (gdb) frame 0
>     #0  0x0000000000450285 in linker_append_elf_syms (linker=0x4feda0, obj=0x7fffffffe100) at linker.c:1296
>     1296		Elf64_Sym *sym = symtab->data->d_buf;
> 
> Signed-off-by: Rong Tao <rongtao@...tc.cn>

Tested-by: Quentin Monnet <qmo@...nel.org>
Reviewed-by: Quentin Monnet <qmo@...nel.org>

Thank you!