bpf: Introduce bpf_arch_text_invalidate for bpf_prog_pack

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

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index a2b6d19..f298b18 100644 (file)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -228,6 +228,11 @@ static void jit_fill_hole(void *area, unsigned int size)
        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 */
 

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index cc4d5e3..a9b1875 100644 (file)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2365,6 +2365,7 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
                       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);

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 2d0c9d4..cacd868 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -968,6 +968,9 @@ static void bpf_prog_pack_free(struct bpf_binary_header *hdr)
        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 *dst, void *src, size_t len)
        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);