| 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
| ||
|
Message-ID: <YxMr7hIXsNcWAiN5@kernel.org>
Date: Sat, 3 Sep 2022 13:26:54 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: linux-sgx@...r.kernel.org
Cc: Haitao Huang <haitao.huang@...ux.intel.com>,
Vijay Dhanraj <vijay.dhanraj@...el.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Paul Menzel <pmenzel@...gen.mpg.de>, stable@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
"H. Peter Anvin" <hpa@...or.com>,
"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86/sgx: Do not fail on incomplete sanitization on
premature stop of ksgxd
On Sat, Sep 03, 2022 at 09:01:07AM +0300, Jarkko Sakkinen wrote:
> Unsanitized pages trigger WARN_ON() unconditionally, which can panic the
> whole computer, if /proc/sys/kernel/panic_on_warn is set.
>
> In sgx_init(), if misc_register() fails or misc_register() succeeds but
> neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be
> prematurely stopped. This may leave unsanitized pages, which will result a
> false warning.
>
> Refine __sgx_sanitize_pages() to return:
>
> 1. Zero when the sanitization process is complete or ksgxd has been
> requested to stop.
> 2. The number of unsanitized pages otherwise.
>
> Use the return value as the criteria for triggering output, and tone down
> the output to pr_err() to prevent the whole system to be taken down if for
> some reason sanitization process does not complete.
>
> Link: https://lore.kernel.org/linux-sgx/20220825051827.246698-1-jarkko@kernel.org/T/#u
> Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list")
> Cc: stable@...r.kernel.org # v5.13+
> Reported-by: Paul Menzel <pmenzel@...gen.mpg.de>
> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> ---
> v7:
> - Rewrote commit message.
> - Do not return -ECANCELED on premature stop. Instead use zero both
> premature stop and complete sanitization.
>
> v6:
> - Address Reinette's feedback:
> https://lore.kernel.org/linux-sgx/Yw6%2FiTzSdSw%2FY%2FVO@kernel.org/
>
> v5:
> - Add the klog dump and sysctl option to the commit message.
>
> v4:
> - Explain expectations for dirty_page_list in the function header, instead
> of an inline comment.
> - Improve commit message to explain the conditions better.
> - Return the number of pages left dirty to ksgxd() and print warning after
> the 2nd call, if there are any.
>
> v3:
> - Remove WARN_ON().
> - Tuned comments and the commit message a bit.
>
> v2:
> - Replaced WARN_ON() with optional pr_info() inside
> __sgx_sanitize_pages().
> - Rewrote the commit message.
> - Added the fixes tag.
> ---
> arch/x86/kernel/cpu/sgx/main.c | 33 ++++++++++++++++++++++++++-------
> 1 file changed, 26 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c
> index 515e2a5f25bb..c0a5ce19c608 100644
> --- a/arch/x86/kernel/cpu/sgx/main.c
> +++ b/arch/x86/kernel/cpu/sgx/main.c
> @@ -49,17 +49,23 @@ static LIST_HEAD(sgx_dirty_page_list);
> * Reset post-kexec EPC pages to the uninitialized state. The pages are removed
> * from the input list, and made available for the page allocator. SECS pages
> * prepending their children in the input list are left intact.
> + *
> + * Contents of the @dirty_page_list must be thread-local, i.e.
> + * not shared by multiple threads.
> + *
> + * Return 0 when sanitization was successful or kthread was stopped, and the
> + * number of unsanitized pages otherwise.
> */
> -static void __sgx_sanitize_pages(struct list_head *dirty_page_list)
> +static unsigned long __sgx_sanitize_pages(struct list_head *dirty_page_list)
> {
> + unsigned long left_dirty = 0;
> struct sgx_epc_page *page;
> LIST_HEAD(dirty);
> int ret;
>
> - /* dirty_page_list is thread-local, no need for a lock: */
> while (!list_empty(dirty_page_list)) {
> if (kthread_should_stop())
> - return;
> + return 0;
>
> page = list_first_entry(dirty_page_list, struct sgx_epc_page, list);
>
> @@ -92,12 +98,14 @@ static void __sgx_sanitize_pages(struct list_head *dirty_page_list)
> } else {
> /* The page is not yet clean - move to the dirty list. */
> list_move_tail(&page->list, &dirty);
> + left_dirty++;
> }
>
> cond_resched();
> }
>
> list_splice(&dirty, dirty_page_list);
> + return left_dirty;
> }
>
> static bool sgx_reclaimer_age(struct sgx_epc_page *epc_page)
> @@ -388,17 +396,28 @@ void sgx_reclaim_direct(void)
>
> static int ksgxd(void *p)
> {
> + unsigned long left_dirty;
> +
> set_freezable();
>
> /*
> * Sanitize pages in order to recover from kexec(). The 2nd pass is
> * required for SECS pages, whose child pages blocked EREMOVE.
> */
> - __sgx_sanitize_pages(&sgx_dirty_page_list);
> - __sgx_sanitize_pages(&sgx_dirty_page_list);
> + left_dirty = __sgx_sanitize_pages(&sgx_dirty_page_list);
> + pr_debug("%ld unsanitized pages\n", left_dirty);
%lu
>
> - /* sanity check: */
> - WARN_ON(!list_empty(&sgx_dirty_page_list));
> + left_dirty = __sgx_sanitize_pages(&sgx_dirty_page_list);
> + /*
> + * Never expected to happen in a working driver. If it happens the bug
> + * is expected to be in the sanitization process, but successfully
> + * sanitized pages are still valid and driver can be used and most
> + * importantly debugged without issues. To put short, the global state
> + * of kernel is not corrupted so no reason to do any more complicated
> + * rollback.
> + */
> + if (left_dirty)
> + pr_err("%ld unsanitized pages\n", left_dirty);
%lu
>
> while (!kthread_should_stop()) {
> if (try_to_freeze())
> --
> 2.37.2
>
BR, Jarkko
Powered by blists - more mailing lists