bpf, x86: fix freeing of not-finalized bpf_prog_pack

syzbot reported a few issues with bpf_prog_pack [1], [2]. This only happens
with multiple subprogs. In jit_subprogs(), we first call bpf_int_jit_compile()
on each sub program. And then, we call it on each sub program again. jit_data
is not freed in the first call of bpf_int_jit_compile(). Similarly we don't
call bpf_jit_binary_pack_finalize() in the first call of bpf_int_jit_compile().

If bpf_int_jit_compile() failed for one sub program, we will call
bpf_jit_binary_pack_finalize() for this sub program. However, we don't have a
chance to call it for other sub programs. Then we will hit "goto out_free" in
jit_subprogs(), and call bpf_jit_free on some subprograms that haven't got
bpf_jit_binary_pack_finalize() yet.

At this point, bpf_jit_binary_pack_free() is called and the whole 2MB page is
freed erroneously.

Fix this with a custom bpf_jit_free() for x86_64, which calls
bpf_jit_binary_pack_finalize() if necessary. Also, with custom
bpf_jit_free(), bpf_prog_aux->use_bpf_prog_pack is not needed any more,
remove it.

Fixes: 1022a5498f6f ("bpf, x86_64: Use bpf_jit_binary_pack_alloc")
[1] https://syzkaller.appspot.com/bug?extid=2f649ec6d2eea1495a8f
[2] https://syzkaller.appspot.com/bug?extid=87f65c75f4a72db05445
Reported-by: syzbot+2f649ec6d2eea1495a8f@syzkaller.appspotmail.com
Reported-by: syzbot+87f65c75f4a72db05445@syzkaller.appspotmail.com
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20220706002612.4013790-1-song@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 12 insertions, 17 deletions

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 805c2ad5c793..cfb8a50a9f12 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -650,12 +650,6 @@ static bool bpf_prog_kallsyms_candidate(const struct bpf_prog *fp)
 	return fp->jited && !bpf_prog_was_classic(fp);
 }
 
-static bool bpf_prog_kallsyms_verify_off(const struct bpf_prog *fp)
-{
-	return list_empty(&fp->aux->ksym.lnode) ||
-	       fp->aux->ksym.lnode.prev == LIST_POISON2;
-}
-
 void bpf_prog_kallsyms_add(struct bpf_prog *fp)
 {
 	if (!bpf_prog_kallsyms_candidate(fp) ||
@@ -1153,7 +1147,6 @@ int bpf_jit_binary_pack_finalize(struct bpf_prog *prog,
 		bpf_prog_pack_free(ro_header);
 		return PTR_ERR(ptr);
 	}
-	prog->aux->use_bpf_prog_pack = true;
 	return 0;
 }
 
@@ -1177,17 +1170,23 @@ void bpf_jit_binary_pack_free(struct bpf_binary_header *ro_header,
 	bpf_jit_uncharge_modmem(size);
 }
 
+struct bpf_binary_header *
+bpf_jit_binary_pack_hdr(const struct bpf_prog *fp)
+{
+	unsigned long real_start = (unsigned long)fp->bpf_func;
+	unsigned long addr;
+
+	addr = real_start & BPF_PROG_CHUNK_MASK;
+	return (void *)addr;
+}
+
 static inline struct bpf_binary_header *
 bpf_jit_binary_hdr(const struct bpf_prog *fp)
 {
 	unsigned long real_start = (unsigned long)fp->bpf_func;
 	unsigned long addr;
 
-	if (fp->aux->use_bpf_prog_pack)
-		addr = real_start & BPF_PROG_CHUNK_MASK;
-	else
-		addr = real_start & PAGE_MASK;
-
+	addr = real_start & PAGE_MASK;
 	return (void *)addr;
 }
 
@@ -1200,11 +1199,7 @@ void __weak bpf_jit_free(struct bpf_prog *fp)
 	if (fp->jited) {
 		struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
 
-		if (fp->aux->use_bpf_prog_pack)
-			bpf_jit_binary_pack_free(hdr, NULL /* rw_buffer */);
-		else
-			bpf_jit_binary_free(hdr);
-
+		bpf_jit_binary_free(hdr);
 		WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
 	}