From: Song Liu <song@kernel.org>
Date: Fri, 20 May 2022 16:57:53 -0700
Subject: bpf: Introduce bpf_arch_text_invalidate for bpf_prog_pack
Patch-mainline: v5.19-rc1
Git-commit: fe736565efb775620dbcf3c459c1cd80d3e868da
References: jsc#PED-1377

Introduce bpf_arch_text_invalidate and use it to fill unused part of the
bpf_prog_pack with illegal instructions when a BPF program is freed.

Fixes: 57631054fae6 ("bpf: Introduce bpf_prog_pack allocator")
Fixes: 33c9805860e5 ("bpf: Introduce bpf_jit_binary_pack_[alloc|finalize|free]")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220520235758.1858153-4-song@kernel.org
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 arch/x86/net/bpf_jit_comp.c |    5 +++++
 include/linux/bpf.h         |    1 +
 kernel/bpf/core.c           |    8 ++++++++
 3 files changed, 14 insertions(+)

--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -222,6 +222,11 @@ static void jit_fill_hole(void *area, un
 	memset(area, 0xcc, size);
 }
 
+int bpf_arch_text_invalidate(void *dst, size_t len)
+{
+	return IS_ERR_OR_NULL(text_poke_set(dst, 0xcc, len));
+}
+
 struct jit_context {
 	int cleanup_addr; /* Epilogue code offset */
 
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2368,6 +2368,7 @@ int bpf_arch_text_poke(void *ip, enum bp
 		       void *addr1, void *addr2);
 
 void *bpf_arch_text_copy(void *dst, void *src, size_t len);
+int bpf_arch_text_invalidate(void *dst, size_t len);
 
 struct btf_id_set;
 bool btf_id_set_contains(const struct btf_id_set *set, u32 id);
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -968,6 +968,9 @@ static void bpf_prog_pack_free(struct bp
 	nbits = BPF_PROG_SIZE_TO_NBITS(hdr->size);
 	pos = ((unsigned long)hdr - (unsigned long)pack_ptr) >> BPF_PROG_CHUNK_SHIFT;
 
+	WARN_ONCE(bpf_arch_text_invalidate(hdr, hdr->size),
+		  "bpf_prog_pack bug: missing bpf_arch_text_invalidate?\n");
+
 	bitmap_clear(pack->bitmap, pos, nbits);
 	if (bitmap_find_next_zero_area(pack->bitmap, bpf_prog_chunk_count(), 0,
 				       bpf_prog_chunk_count(), 0) == 0) {
@@ -2740,6 +2743,11 @@ void * __weak bpf_arch_text_copy(void *d
 	return ERR_PTR(-ENOTSUPP);
 }
 
+int __weak bpf_arch_text_invalidate(void *dst, size_t len)
+{
+	return -ENOTSUPP;
+}
+
 DEFINE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
 EXPORT_SYMBOL(bpf_stats_enabled_key);