linux-kernel - Re: [tip:x86/boot 10/10] arch/x86/boot/compressed/sev-handle-vc.c:104 do_boot_stage2_vc() error: we previously assumed 'boot

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAMj1kXHyVh7KwNyekd8ZAATufnMHyzyMismVf2xW8F=LfBJviQ@mail.gmail.com>
Date: Sat, 10 May 2025 09:57:23 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: oe-kbuild@...ts.linux.dev, lkp@...el.com, oe-kbuild-all@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, x86@...nel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [tip:x86/boot 10/10] arch/x86/boot/compressed/sev-handle-vc.c:104
 do_boot_stage2_vc() error: we previously assumed 'boot_ghcb' could be null
 (see line 101)

Hi Dan,

On Sat, 10 May 2025 at 09:43, Dan Carpenter <dan.carpenter@...aro.org> wrote:
>
> Hi Ard,
>
> FYI, the error/warning was bisected to this commit, please ignore it if it's irrelevant.
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/boot
> head:   ed4d95d033e359f9445e85bf5a768a5859a5830b
> commit: ed4d95d033e359f9445e85bf5a768a5859a5830b [10/10] x86/sev: Disentangle #VC handling code from startup code
> config: x86_64-randconfig-161-20250510 (https://download.01.org/0day-ci/archive/20250510/202505100719.9pE7wDfB-lkp@intel.com/config)
> compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@...el.com>
> | Reported-by: Dan Carpenter <dan.carpenter@...aro.org>
> | Closes: https://lore.kernel.org/r/202505100719.9pE7wDfB-lkp@intel.com/
>
> smatch warnings:
> arch/x86/boot/compressed/sev-handle-vc.c:104 do_boot_stage2_vc() error: we previously assumed 'boot_ghcb' could be null (see line 101)
>
> vim +/boot_ghcb +104 arch/x86/boot/compressed/sev-handle-vc.c
>
> ed4d95d033e359 Ard Biesheuvel 2025-05-04   96  void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
> ed4d95d033e359 Ard Biesheuvel 2025-05-04   97  {
> ed4d95d033e359 Ard Biesheuvel 2025-05-04   98   struct es_em_ctxt ctxt;
> ed4d95d033e359 Ard Biesheuvel 2025-05-04   99   enum es_result result;
> ed4d95d033e359 Ard Biesheuvel 2025-05-04  100
> ed4d95d033e359 Ard Biesheuvel 2025-05-04 @101   if (!boot_ghcb && !early_setup_ghcb())
>                                                     ^^^^^^^^^^
> Check for NULL.  Should the && be ||?
>
> ed4d95d033e359 Ard Biesheuvel 2025-05-04  102           sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ);
> ed4d95d033e359 Ard Biesheuvel 2025-05-04  103
> ed4d95d033e359 Ard Biesheuvel 2025-05-04 @104   vc_ghcb_invalidate(boot_ghcb);
>                                                                    ^^^^^^^^^
> Unchecked dereference.
>

On success, early_setup_ghcb() will assign boot_ghcb, and so it is
only called if it was unset.

The logic is a bit clunky here: for clarity, it could be rewritten as

if (!boot_ghcb) {
  early_setup_ghcb();
  if (!boot_ghcb)
    sev_es_terminate(...);
}