Commit 0b31a3ce authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

s390/mm/fault: convert do_secure_storage_access() from follow_page() to folio_walk 

Let's get rid of another follow_page() user and perform the conversion
under PTL: Note that this is also what follow_page_pte() ends up doing.

Unfortunately we cannot currently optimize out the additional reference,
because arch_make_folio_accessible() must be called with a raised refcount
to protect against concurrent conversion to secure.  We can just move the
arch_make_folio_accessible() under the PTL, like follow_page_pte() would.

We'll effectively drop the "writable" check implied by FOLL_WRITE:
follow_page_pte() would also not check that when calling
arch_make_folio_accessible(), so there is no good reason for doing that
here.

We'll lose the secretmem check from follow_page() as well, about which we
shouldn't really care.

Link: https://lkml.kernel.org/r/20240802155524.517137-10-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 85a7e543

arch/s390/mm/fault.c

+10 −6
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#include <linux/uaccess.h>

#include <linux/hugetlb.h>

#include <linux/kfence.h>

#include <linux/pagewalk.h>

#include <asm/asm-extable.h>

#include <asm/asm-offsets.h>

#include <asm/ptrace.h>
@@ -492,9 +493,9 @@ void do_secure_storage_access(struct pt_regs *regs) 
	union teid teid = { .val = regs->int_parm_long };

	unsigned long addr = get_fault_address(regs);

	struct vm_area_struct *vma;

	struct folio_walk fw;

	struct mm_struct *mm;

	struct folio *folio;

	struct page *page;

	struct gmap *gmap;

	int rc;
@@ -536,15 +537,18 @@ void do_secure_storage_access(struct pt_regs *regs) 
		vma = find_vma(mm, addr);

		if (!vma)

			return handle_fault_error(regs, SEGV_MAPERR);

		page = follow_page(vma, addr, FOLL_WRITE | FOLL_GET);

		if (IS_ERR_OR_NULL(page)) {

		folio = folio_walk_start(&fw, vma, addr, 0);

		if (!folio) {

			mmap_read_unlock(mm);

			break;

		}

		folio = page_folio(page);

		if (arch_make_folio_accessible(folio))

			send_sig(SIGSEGV, current, 0);

		/* arch_make_folio_accessible() needs a raised refcount. */

		folio_get(folio);

		rc = arch_make_folio_accessible(folio);

		folio_put(folio);

		folio_walk_end(&fw, vma);

		if (rc)

			send_sig(SIGSEGV, current, 0);

		mmap_read_unlock(mm);

		break;

	case KERNEL_FAULT: