| Message ID | 20210924023725.70228-1-memxor@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf] libbpf: Fix segfault in static linker for objects without BTF | expand |
On Thu, Sep 23, 2021 at 7:39 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote: > > When a BPF object is compiled without BTF info (without -g), > trying to link such objects using bpftool causes a SIGSEGV due to > btf__get_nr_types accessing obj->btf which is NULL. Fix this by > checking for the NULL pointer, and return error. > > Reproducer: > $ cat a.bpf.c > extern int foo(void); > int bar(void) { return foo(); } > $ cat b.bpf.c > int foo(void) { return 0; } > $ clang -O2 -target bpf -c a.bpf.c > $ clang -O2 -target bpf -c b.bpf.c > $ bpftool gen obj out a.bpf.o b.bpf.o > Segmentation fault (core dumped) > > After fix: > $ bpftool gen obj out a.bpf.o b.bpf.o > libbpf: failed to find BTF info for object 'a.bpf.o' > Error: failed to link 'a.bpf.o': Unknown error -22 (-22) > > Fixes: a46349227cd8 (libbpf: Add linker extern resolution support for functions and global variables) > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> > --- > tools/lib/bpf/linker.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > Applied to bpf, thanks. [...]
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index 10911a8cad0f..2df880cefdae 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c @@ -1649,11 +1649,17 @@ static bool btf_is_non_static(const struct btf_type *t) static int find_glob_sym_btf(struct src_obj *obj, Elf64_Sym *sym, const char *sym_name, int *out_btf_sec_id, int *out_btf_id) { - int i, j, n = btf__get_nr_types(obj->btf), m, btf_id = 0; + int i, j, n, m, btf_id = 0; const struct btf_type *t; const struct btf_var_secinfo *vi; const char *name; + if (!obj->btf) { + pr_warn("failed to find BTF info for object '%s'\n", obj->filename); + return -EINVAL; + } + + n = btf__get_nr_types(obj->btf); for (i = 1; i <= n; i++) { t = btf__type_by_id(obj->btf, i);
When a BPF object is compiled without BTF info (without -g), trying to link such objects using bpftool causes a SIGSEGV due to btf__get_nr_types accessing obj->btf which is NULL. Fix this by checking for the NULL pointer, and return error. Reproducer: $ cat a.bpf.c extern int foo(void); int bar(void) { return foo(); } $ cat b.bpf.c int foo(void) { return 0; } $ clang -O2 -target bpf -c a.bpf.c $ clang -O2 -target bpf -c b.bpf.c $ bpftool gen obj out a.bpf.o b.bpf.o Segmentation fault (core dumped) After fix: $ bpftool gen obj out a.bpf.o b.bpf.o libbpf: failed to find BTF info for object 'a.bpf.o' Error: failed to link 'a.bpf.o': Unknown error -22 (-22) Fixes: a46349227cd8 (libbpf: Add linker extern resolution support for functions and global variables) Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> --- tools/lib/bpf/linker.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) -- 2.33.0