libbpf: Fix using invalidated memory in bpf_linker

[ Upstream commit 593835377f ]

add_dst_sec() can invalidate bpf_linker's section index making
dst_symtab pointer pointing into unallocated memory. Reinitialize
dst_symtab pointer on each iteration to make sure it's always valid.

Fixes: faf6ed321c ("libbpf: Add BPF static linker APIs")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211124002325.1737739-7-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Andrii Nakryiko 2021-11-23 16:23:18 -08:00 committed by Greg Kroah-Hartman
parent 9b616ae0bf
commit ef89212783

View File

@ -2001,7 +2001,7 @@ add_sym:
static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *obj)
{
struct src_sec *src_symtab = &obj->secs[obj->symtab_sec_idx];
struct dst_sec *dst_symtab = &linker->secs[linker->symtab_sec_idx];
struct dst_sec *dst_symtab;
int i, err;
for (i = 1; i < obj->sec_cnt; i++) {
@ -2034,6 +2034,9 @@ static int linker_append_elf_relos(struct bpf_linker *linker, struct src_obj *ob
return -1;
}
/* add_dst_sec() above could have invalidated linker->secs */
dst_symtab = &linker->secs[linker->symtab_sec_idx];
/* shdr->sh_link points to SYMTAB */
dst_sec->shdr->sh_link = linker->symtab_sec_idx;