CVE-2022-50168

In the Linux kernel, the following vulnerability has been resolved:

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 dont 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 dont 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 havent 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.

[1] https://syzkaller.appspot.com/bug?extid=2f649ec6d2eea1495a8f [2] https://syzkaller.appspot.com/bug?extid=87f65c75f4a72db05445

Affected Software

References

• https://git.kernel.org/stable/c/1d5f82d9dd477d5c66e0214a68c3e4f308eadd6d
• https://git.kernel.org/stable/c/60e66074812dde9cde3d99cdd3caa9e40f1a4516
• https://git.kernel.org/stable/c/f91ce608a79c0db3e72bd63c23e011a9ebc31505