From: Rong Tao <rongtao@xxxxxxxx>
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.
$ sudo ./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@xxxxxxxx>
---
tools/bpf/bpftool/gen.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 5a4d3240689e..4cd135726758 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -1896,6 +1896,11 @@ static int do_object(int argc, char **argv)
while (argc) {
file = GET_ARG();
+ if (!strcmp(file, output_file)) {
+ p_err("Input/Output file couldn't be same.");
+ goto out;
+ }
+
err = bpf_linker__add_file(linker, file, NULL);
if (err) {
p_err("failed to link '%s': %s (%d)", file, strerror(errno), errno);
--
2.47.1
