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Date: Fri, 26 Aug 2022 19:21:44 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Jarkko Sakkinen <jarkko@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
linux-sgx@...r.kernel.org
Cc: Haitao Huang <haitao.huang@...ux.intel.com>,
Reinette Chatre <reinette.chatre@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] x86/sgx: Do not consider unsanitized pages an error
Dear Jarkko,
Am 26.08.22 um 14:51 schrieb Paul Menzel:
[…]
> Am 26.08.22 um 03:41 schrieb Jarkko Sakkinen:
>> In sgx_init(), if misc_register() for the provision device fails, and
>> neither sgx_drv_init() nor sgx_vepc_init() succeeds, then ksgxd will be
>> prematurely stopped.
>>
>> This triggers WARN_ON() because sgx_dirty_page_list ends up being
>> non-empty. Ultimately this can crash the kernel, depending on the kernel
>> command line, which is not correct behavior because SGX driver is not
>> working incorrectly.
>
> Maybe paste the WARN_ON trace, so `git log` can be searched for the
> trace too.
>
>> Print simple warning instead, and improve the output by printing the
>> number of unsanitized pages.
>
> See below, but no warning seems to be logged in my case now. (I should
> test Linus’ current master too.)
Just for the record, the problem still exists in Linus’ master branch:
```
[ 0.000000] Linux version 6.0.0-rc2 (root@...b429beb4a) (gcc (Debian
11.3.0-3) 11.3.0, GNU ld (GNU Binutils for Debian) 2.38) #382 SMP
PREEMPT_DYNAMIC Fri Aug 26 12:52:15 UTC 2022
[ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-6.0.0-rc2
root=UUID=56f398e0-1e25-4fda-aa9f-611dece4b333 ro quiet
module_blacklist=psmouse initcall_debug log_buf_len=4M cryptomgr.notests
[…]
[ 0.268089] calling sgx_init+0x0/0x409 @ 1
[ 0.268103] sgx: EPC section 0x40200000-0x45f7ffff
[ 0.268591] ------------[ cut here ]------------
[ 0.268592] WARNING: CPU: 6 PID: 83 at
arch/x86/kernel/cpu/sgx/main.c:401 ksgxd+0x1b7/0x1d0
[ 0.268598] Modules linked in:
[ 0.268600] CPU: 6 PID: 83 Comm: ksgxd Not tainted 6.0.0-rc2 #382
[ 0.268603] Hardware name: Dell Inc. XPS 13 9370/0RMYH9, BIOS 1.21.0
07/06/2022
[ 0.268604] RIP: 0010:ksgxd+0x1b7/0x1d0
[ 0.268607] Code: ff e9 f2 fe ff ff 48 89 df e8 75 07 0e 00 84 c0 0f
84 c3 fe ff ff 31 ff e8 e6 07 0e 00 84 c0 0f 85 94 fe ff ff e9 af fe ff
ff <0f> 0b e9 7f fe ff ff e8 dd 9c 95 00 66 66 2e 0f 1f 84 00 00 00 00
[ 0.268608] RSP: 0000:ffffb6c7404f3ed8 EFLAGS: 00010287
[ 0.268610] RAX: ffffb6c740431a10 RBX: ffff8dcd8117b400 RCX:
0000000000000000
[ 0.268612] RDX: 0000000080000000 RSI: ffffb6c7404319d0 RDI:
00000000ffffffff
[ 0.268613] RBP: ffff8dcd820a4d80 R08: ffff8dcd820a4180 R09:
ffff8dcd820a4180
[ 0.268614] R10: 0000000000000000 R11: 0000000000000006 R12:
ffffb6c74006bce0
[ 0.268615] R13: ffff8dcd80e63880 R14: ffffffffa8a60f10 R15:
0000000000000000
[ 0.268616] FS: 0000000000000000(0000) GS:ffff8dcf25580000(0000)
knlGS:0000000000000000
[ 0.268617] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 0.268619] CR2: 0000000000000000 CR3: 0000000213410001 CR4:
00000000003706e0
[ 0.268620] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[ 0.268621] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[ 0.268622] Call Trace:
[ 0.268624] <TASK>
[ 0.268627] ? _raw_spin_lock_irqsave+0x24/0x60
[ 0.268632] ? _raw_spin_unlock_irqrestore+0x23/0x40
[ 0.268634] ? __kthread_parkme+0x36/0x90
[ 0.268637] kthread+0xe5/0x110
[ 0.268639] ? kthread_complete_and_exit+0x20/0x20
[ 0.268642] ret_from_fork+0x1f/0x30
[ 0.268647] </TASK>
[ 0.268648] ---[ end trace 0000000000000000 ]---
[ 0.268694] initcall sgx_init+0x0/0x409 returned -19 after 603 usecs
```
Tested-by: Paul Menzel <pmenzel@...gen.mpg.de>
>> Link: https://lore.kernel.org/linux-sgx/20220825051827.246698-1-jarkko@kernel.org/T/#u
>> Reported-by: Paul Menzel <pmenzel@...gen.mpg.de>
>> Fixes: 51ab30eb2ad4 ("x86/sgx: Replace section->init_laundry_list with sgx_dirty_page_list")
>> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
>> ---
>> Cc: Haitao Huang <haitao.huang@...ux.intel.com>
>> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
>> Cc: Reinette Chatre <reinette.chatre@...el.com>
>>
>> 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 | 19 +++++++++++++------
>> 1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/sgx/main.c
>> b/arch/x86/kernel/cpu/sgx/main.c
>> index 515e2a5f25bb..903100fcfce3 100644
>> --- a/arch/x86/kernel/cpu/sgx/main.c
>> +++ b/arch/x86/kernel/cpu/sgx/main.c
>> @@ -49,17 +49,20 @@ 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.
>> */
>> -static void __sgx_sanitize_pages(struct list_head *dirty_page_list)
>> +static int __sgx_sanitize_pages(struct list_head *dirty_page_list)
>> {
>> struct sgx_epc_page *page;
>> + int left_dirty = 0;
>> 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;
>> + break;
>> page = list_first_entry(dirty_page_list, struct
>> sgx_epc_page, list);
>> @@ -92,12 +95,14 @@ 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)
>> @@ -388,6 +393,8 @@ void sgx_reclaim_direct(void)
>> static int ksgxd(void *p)
>> {
>> + int left_dirty;
>> +
>> set_freezable();
>> /*
>> @@ -395,10 +402,10 @@ static int ksgxd(void *p)
>> * required for SECS pages, whose child pages blocked EREMOVE.
>> */
>> __sgx_sanitize_pages(&sgx_dirty_page_list);
>> - __sgx_sanitize_pages(&sgx_dirty_page_list);
>> - /* sanity check: */
>> - WARN_ON(!list_empty(&sgx_dirty_page_list));
>> + left_dirty = __sgx_sanitize_pages(&sgx_dirty_page_list);
>> + if (left_dirty)
>> + pr_warn("%d unsanitized pages\n", left_dirty);
>> while (!kthread_should_stop()) {
>> if (try_to_freeze())
>
> I tested this on top of commit 4c612826bec1 (Merge tag 'net-6.0-rc3' of
> git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net) and the
> warning trace is gone.
>
> [ 0.255192] calling sgx_init+0x0/0x409 @ 1
> [ 0.255207] sgx: EPC section 0x40200000-0x45f7ffff
> [ 0.255747] initcall sgx_init+0x0/0x409 returned -19 after 552 usecs
>
> (OT: If -19 suggests something failed, a message, why sgx_init() failed
> would be nice.)
>
> Please find the whole output of `dmesg` attached.
>
>
> Kind regards,
>
> Paul
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