[PATCH 6.12 450/567] LoongArch: BPF: Zero-extend bpf_tail_call() index

Greg Kroah-Hartman
2026-01-06T17:39:12Z

From: Hengqi Chen <hengqi.chen@gmail.com>

commit eb71f5c433e1c6dff089b315881dec40a88a7baf upstream.

The bpf_tail_call() index should be treated as a u32 value. Let's
zero-extend it to avoid calling wrong BPF progs. See similar fixes
for x86 [1]) and arm64 ([2]) for more details.

[1]: https://github.com/torvalds/linux/commit/90caccdd8cc0215705f18b92771b449b01e2474a
[2]: https://github.com/torvalds/linux/commit/16338a9b3ac30740d49f5dfed81bac0ffa53b9c7

Cc: stable@vger.kernel.org
Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/loongarch/net/bpf_jit.c | 2 ++
1 file changed, 2 insertions(+)

--- a/arch/loongarch/net/bpf_jit.c
+++ b/arch/loongarch/net/bpf_jit.c
@@ -231,6 +231,8 @@ static int emit_bpf_tail_call(struct jit
* goto out;
*/
tc_ninsn = insn ? ctx->offset[insn+1] - ctx->offset[insn] : ctx->offset[0];
+ emit_zext_32(ctx, a2, true);
+
off = offsetof(struct bpf_array, map.max_entries);
emit_insn(ctx, ldwu, t1, a1, off);
/* bgeu $a2, $t1, jmp_offset */