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Message-ID: <d243610c-78df-5e25-cb60-320e7a352d82@redhat.com>
Date: Fri, 14 May 2021 11:27:11 +0200
From: David Hildenbrand <david@...hat.com>
To: Mike Rapoport <rppt@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Alexander Viro <viro@...iv.linux.org.uk>,
Andy Lutomirski <luto@...nel.org>,
Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
Catalin Marinas <catalin.marinas@....com>,
Christopher Lameter <cl@...ux.com>,
Dan Williams <dan.j.williams@...el.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Elena Reshetova <elena.reshetova@...el.com>,
"H. Peter Anvin" <hpa@...or.com>,
Hagen Paul Pfeifer <hagen@...u.net>,
Ingo Molnar <mingo@...hat.com>,
James Bottomley <jejb@...ux.ibm.com>,
Kees Cook <keescook@...omium.org>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Matthew Wilcox <willy@...radead.org>,
Matthew Garrett <mjg59@...f.ucam.org>,
Mark Rutland <mark.rutland@....com>,
Michal Hocko <mhocko@...e.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Michael Kerrisk <mtk.manpages@...il.com>,
Palmer Dabbelt <palmer@...belt.com>,
Palmer Dabbelt <palmerdabbelt@...gle.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Peter Zijlstra <peterz@...radead.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Rick Edgecombe <rick.p.edgecombe@...el.com>,
Roman Gushchin <guro@...com>,
Shakeel Butt <shakeelb@...gle.com>,
Shuah Khan <shuah@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
Yury Norov <yury.norov@...il.com>, linux-api@...r.kernel.org,
linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
x86@...nel.org
Subject: Re: [PATCH v19 6/8] PM: hibernate: disable when there are active
secretmem users
On 13.05.21 20:47, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
>
> It is unsafe to allow saving of secretmem areas to the hibernation
> snapshot as they would be visible after the resume and this essentially
> will defeat the purpose of secret memory mappings.
>
> Prevent hibernation whenever there are active secret memory users.
>
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Christopher Lameter <cl@...ux.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Elena Reshetova <elena.reshetova@...el.com>
> Cc: Hagen Paul Pfeifer <hagen@...u.net>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: James Bottomley <jejb@...ux.ibm.com>
> Cc: "Kirill A. Shutemov" <kirill@...temov.name>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: Michael Kerrisk <mtk.manpages@...il.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Palmer Dabbelt <palmerdabbelt@...gle.com>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Rick Edgecombe <rick.p.edgecombe@...el.com>
> Cc: Roman Gushchin <guro@...com>
> Cc: Shakeel Butt <shakeelb@...gle.com>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Tycho Andersen <tycho@...ho.ws>
> Cc: Will Deacon <will@...nel.org>
> ---
> include/linux/secretmem.h | 6 ++++++
> kernel/power/hibernate.c | 5 ++++-
> mm/secretmem.c | 15 +++++++++++++++
> 3 files changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/secretmem.h b/include/linux/secretmem.h
> index e617b4afcc62..21c3771e6a56 100644
> --- a/include/linux/secretmem.h
> +++ b/include/linux/secretmem.h
> @@ -30,6 +30,7 @@ static inline bool page_is_secretmem(struct page *page)
> }
>
> bool vma_is_secretmem(struct vm_area_struct *vma);
> +bool secretmem_active(void);
>
> #else
>
> @@ -43,6 +44,11 @@ static inline bool page_is_secretmem(struct page *page)
> return false;
> }
>
> +static inline bool secretmem_active(void)
> +{
> + return false;
> +}
> +
> #endif /* CONFIG_SECRETMEM */
>
> #endif /* _LINUX_SECRETMEM_H */
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index da0b41914177..559acef3fddb 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -31,6 +31,7 @@
> #include <linux/genhd.h>
> #include <linux/ktime.h>
> #include <linux/security.h>
> +#include <linux/secretmem.h>
> #include <trace/events/power.h>
>
> #include "power.h"
> @@ -81,7 +82,9 @@ void hibernate_release(void)
>
> bool hibernation_available(void)
> {
> - return nohibernate == 0 && !security_locked_down(LOCKDOWN_HIBERNATION);
> + return nohibernate == 0 &&
> + !security_locked_down(LOCKDOWN_HIBERNATION) &&
> + !secretmem_active();
> }
>
> /**
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index 1ae50089adf1..7c2499e4de22 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -40,6 +40,13 @@ module_param_named(enable, secretmem_enable, bool, 0400);
> MODULE_PARM_DESC(secretmem_enable,
> "Enable secretmem and memfd_secret(2) system call");
>
> +static atomic_t secretmem_users;
> +
> +bool secretmem_active(void)
> +{
> + return !!atomic_read(&secretmem_users);
> +}
> +
> static vm_fault_t secretmem_fault(struct vm_fault *vmf)
> {
> struct address_space *mapping = vmf->vma->vm_file->f_mapping;
> @@ -94,6 +101,12 @@ static const struct vm_operations_struct secretmem_vm_ops = {
> .fault = secretmem_fault,
> };
>
> +static int secretmem_release(struct inode *inode, struct file *file)
> +{
> + atomic_dec(&secretmem_users);
> + return 0;
> +}
> +
> static int secretmem_mmap(struct file *file, struct vm_area_struct *vma)
> {
> unsigned long len = vma->vm_end - vma->vm_start;
> @@ -116,6 +129,7 @@ bool vma_is_secretmem(struct vm_area_struct *vma)
> }
>
> static const struct file_operations secretmem_fops = {
> + .release = secretmem_release,
> .mmap = secretmem_mmap,
> };
>
> @@ -202,6 +216,7 @@ SYSCALL_DEFINE1(memfd_secret, unsigned int, flags)
> file->f_flags |= O_LARGEFILE;
>
> fd_install(fd, file);
> + atomic_inc(&secretmem_users);
> return fd;
>
> err_put_fd:
>
It looks a bit racy, but I guess we don't really care about these corner
cases.
Acked-by: David Hildenbrand <david@...hat.com>
--
Thanks,
David / dhildenb
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