From: Hou Tao <houtao1@huawei.com>
Date: Wed, 9 Mar 2022 20:33:18 +0800
Subject: bpf, x86: Fall back to interpreter mode when extra pass fails
Patch-mainline: v5.18-rc1
Git-commit: 73e14451f39e54f83ea3badb6d6b8a423f901845
References: jsc#PED-1377

Extra pass for subprog jit may fail (e.g. due to bpf_jit_harden race),
but bpf_func is not cleared for the subprog and jit_subprogs will
succeed. The running of the bpf program may lead to oops because the
memory for the jited subprog image has already been freed.

So fall back to interpreter mode by clearing bpf_func/jited/jited_len
when extra pass fails.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220309123321.2400262-2-houtao1@huawei.com
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 arch/x86/net/bpf_jit_comp.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -2335,7 +2335,13 @@ out_image:
 						   sizeof(rw_header->size));
 				bpf_jit_binary_pack_free(header, rw_header);
 			}
+			/* Fall back to interpreter mode */
 			prog = orig_prog;
+			if (extra_pass) {
+				prog->bpf_func = NULL;
+				prog->jited = 0;
+				prog->jited_len = 0;
+			}
 			goto out_addrs;
 		}
 		if (image) {
@@ -2384,8 +2390,9 @@ out_image:
 			 * Both cases are serious bugs and justify WARN_ON.
 			 */
 			if (WARN_ON(bpf_jit_binary_pack_finalize(prog, header, rw_header))) {
-				prog = orig_prog;
-				goto out_addrs;
+				/* header has been freed */
+				header = NULL;
+				goto out_image;
 			}
 
 			bpf_tail_call_direct_fixup(prog);