On Thu, May 13, 2021 at 09:47:32PM +0300, Mike Rapoport wrote:
From: Mike Rapoport rppt@linux.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.
Have we thought about how this is going to work in practice, e.g. on mobile systems? It seems to me that there are a variety of common applications which might want to use this which people don't expect to inhibit hibernate (e.g. authentication agents, web browsers).
Are we happy to say that any userspace application can incidentally inhibit hibernate?
Thanks, Mark.
Signed-off-by: Mike Rapoport rppt@linux.ibm.com Cc: Alexander Viro viro@zeniv.linux.org.uk Cc: Andy Lutomirski luto@kernel.org Cc: Arnd Bergmann arnd@arndb.de Cc: Borislav Petkov bp@alien8.de Cc: Catalin Marinas catalin.marinas@arm.com Cc: Christopher Lameter cl@linux.com Cc: Dan Williams dan.j.williams@intel.com Cc: Dave Hansen dave.hansen@linux.intel.com Cc: David Hildenbrand david@redhat.com Cc: Elena Reshetova elena.reshetova@intel.com Cc: Hagen Paul Pfeifer hagen@jauu.net Cc: "H. Peter Anvin" hpa@zytor.com Cc: Ingo Molnar mingo@redhat.com Cc: James Bottomley jejb@linux.ibm.com Cc: "Kirill A. Shutemov" kirill@shutemov.name Cc: Mark Rutland mark.rutland@arm.com Cc: Matthew Wilcox willy@infradead.org Cc: Michael Kerrisk mtk.manpages@gmail.com Cc: Palmer Dabbelt palmer@dabbelt.com Cc: Palmer Dabbelt palmerdabbelt@google.com Cc: Paul Walmsley paul.walmsley@sifive.com Cc: Peter Zijlstra peterz@infradead.org Cc: Rick Edgecombe rick.p.edgecombe@intel.com Cc: Roman Gushchin guro@fb.com Cc: Shakeel Butt shakeelb@google.com Cc: Shuah Khan shuah@kernel.org Cc: Thomas Gleixner tglx@linutronix.de Cc: Tycho Andersen tycho@tycho.ws Cc: Will Deacon will@kernel.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: -- 2.28.0