From: Jarkko Sakkinen <jarkko@kernel.org>
To: Sean Christopherson <seanjc@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
linux-sgx@vger.kernel.org, stable@vger.kernel.org,
Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Jethro Beekman <jethro@fortanix.com>,
Serge Ayoun <serge.ayoun@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/5] x86/sgx: Fix a resource leak in sgx_init()
Date: Wed, 10 Mar 2021 23:52:40 +0200 [thread overview]
Message-ID: <YEk/qNwCkL63CYFy@kernel.org> (raw)
In-Reply-To: <YEjqieABvycpGn0h@google.com>
On Wed, Mar 10, 2021 at 07:49:29AM -0800, Sean Christopherson wrote:
> On Wed, Mar 10, 2021, Jarkko Sakkinen wrote:
> > On Wed, Mar 03, 2021 at 08:56:52AM -0800, Dave Hansen wrote:
> > > On 3/3/21 7:03 AM, Jarkko Sakkinen wrote:
> > > > If sgx_page_cache_init() fails in the middle, a trivial return
> > > > statement causes unused memory and virtual address space reserved for
> > > > the EPC section, not freed. Fix this by using the same rollback, as
> > > > when sgx_page_reclaimer_init() fails.
> > > ...
> > > > @@ -708,8 +708,10 @@ static int __init sgx_init(void)
> > > > if (!cpu_feature_enabled(X86_FEATURE_SGX))
> > > > return -ENODEV;
> > > >
> > > > - if (!sgx_page_cache_init())
> > > > - return -ENOMEM;
> > > > + if (!sgx_page_cache_init()) {
> > > > + ret = -ENOMEM;
> > > > + goto err_page_cache;
> > > > + }
> > >
> > >
> > > Currently, the only way sgx_page_cache_init() can fail is in the case
> > > that there are no sections:
> > >
> > > if (!sgx_nr_epc_sections) {
> > > pr_err("There are zero EPC sections.\n");
> > > return false;
> > > }
> > >
> > > That only happened if all sgx_setup_epc_section() calls failed.
> > > sgx_setup_epc_section() never both allocates memory with vmalloc for
> > > section->pages *and* fails. If sgx_setup_epc_section() has a successful
> > > memremap() but a failed vmalloc(), it cleans up with memunmap().
> > >
> > > In other words, I see how this _looks_ like a memory leak from
> > > sgx_init(), but I don't see an actual leak in practice.
> > >
> > > Am I missing something?
> >
> > In sgx_setup_epc_section():
> >
> >
> > section->pages = vmalloc(nr_pages * sizeof(struct sgx_epc_page));
> > if (!section->pages) {
> > memunmap(section->virt_addr);
> > return false;
> > }
> >
> > I.e. this rollback does not happen without this fix applied:
> >
> > for (i = 0; i < sgx_nr_epc_sections; i++) {
> > vfree(sgx_epc_sections[i].pages);
> > memunmap(sgx_epc_sections[i].virt_addr);
> > }
>
> Dave is pointing out that sgx_page_cache_init() fails if and only if _all_
> sections fail sgx_setup_epc_section(), and if all sections fail then
> sgx_nr_epc_sections is '0' and the above is a nop.
>
> That behavior is by design, as we didn't want to kill SGX if a single section
> failed to initialize for whatever reason.
My bad. You're correct. I got mixed up by the rollback :-) Thanks!
I'll just drop the whole patch.
/Jarkko
next prev parent reply other threads:[~2021-03-10 21:54 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210303150323.433207-1-jarkko@kernel.org>
2021-03-03 15:03 ` [PATCH v3 1/5] x86/sgx: Fix a resource leak in sgx_init() Jarkko Sakkinen
2021-03-03 16:56 ` Dave Hansen
2021-03-10 15:00 ` Jarkko Sakkinen
2021-03-10 15:49 ` Sean Christopherson
2021-03-10 21:52 ` Jarkko Sakkinen [this message]
2021-03-03 15:03 ` [PATCH v3 2/5] x86/sgx: Use sgx_free_epc_page() in sgx_reclaim_pages() Jarkko Sakkinen
2021-03-03 16:59 ` Dave Hansen
2021-03-10 15:11 ` Jarkko Sakkinen
2021-03-10 15:55 ` Dave Hansen
2021-03-10 21:56 ` Jarkko Sakkinen
2021-03-10 20:36 ` Kai Huang
2021-03-10 22:10 ` Jarkko Sakkinen
2021-03-10 22:12 ` Jarkko Sakkinen
2021-03-10 22:35 ` Jarkko Sakkinen
2021-03-10 22:43 ` Kai Huang
2021-03-10 22:52 ` Kai Huang
2021-03-03 15:03 ` [PATCH v3 3/5] x86/sgx: Replace section->init_laundry_list with a temp list Jarkko Sakkinen
2021-03-03 18:02 ` Dave Hansen
2021-03-10 14:50 ` Jarkko Sakkinen
2021-03-03 15:03 ` [PATCH v3 4/5] x86/sgx: Replace section->page_list with a global free page list Jarkko Sakkinen
2021-03-03 23:48 ` Dave Hansen
2021-03-10 10:54 ` Jarkko Sakkinen
2021-03-03 15:03 ` [PATCH v3 5/5] x86/sgx: Add a basic NUMA allocation scheme to sgx_alloc_epc_page() Jarkko Sakkinen
2021-03-04 0:20 ` Dave Hansen
2021-03-10 11:30 ` Jarkko Sakkinen
2021-03-10 15:44 ` Dave Hansen
2021-03-10 21:48 ` Jarkko Sakkinen
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