From: Yonghong Song yhs@fb.com
[ Upstream commit b58b2b3a31228bd9aaed9b96e9452dafd0d46024 ]
Currently, the 64bit relocation value in the instruction is computed as follows: __u64 imm = insn[0].imm + ((__u64)insn[1].imm << 32)
Suppose insn[0].imm = -1 (0xffffffff) and insn[1].imm = 1. With the above computation, insn[0].imm will first sign-extend to 64bit -1 (0xffffffffFFFFFFFF) and then add 0x1FFFFFFFF, producing incorrect value 0xFFFFFFFF. The correct value should be 0x1FFFFFFFF.
Changing insn[0].imm to __u32 first will prevent 64bit sign extension and fix the issue. Merging high and low 32bit values also changed from '+' to '|' to be consistent with other similar occurences in kernel and libbpf.
Acked-by: Andrii Nakryiko andrii@kernel.org Acked-by: Dave Marchevsky davemarchevsky@fb.com Signed-off-by: Yonghong Song yhs@fb.com Link: https://lore.kernel.org/r/20220607062610.3717378-1-yhs@fb.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/relo_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/lib/bpf/relo_core.c b/tools/lib/bpf/relo_core.c index 4016ed492d0c..1d65b47c0779 100644 --- a/tools/lib/bpf/relo_core.c +++ b/tools/lib/bpf/relo_core.c @@ -1015,7 +1015,7 @@ static int bpf_core_patch_insn(const char *prog_name, struct bpf_insn *insn, return -EINVAL; }
- imm = insn[0].imm + ((__u64)insn[1].imm << 32); + imm = (__u32)insn[0].imm | ((__u64)insn[1].imm << 32); if (res->validate && imm != orig_val) { pr_warn("prog '%s': relo #%d: unexpected insn #%d (LDIMM64) value: got %llu, exp %u -> %u\n", prog_name, relo_idx,