Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 44efbdc4 authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Greg Kroah-Hartman
Browse files

mm, gup: add missing refcount overflow checks on s390 



The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from
overflowing page refcount") was backported to 4.19.y stable as commit
d972ebbf. The backport however missed that in 4.19, there are several
arch-specific gup.c versions with fast gup implementations, so these do not
prevent refcount overflow.

This stable-only commit fixes the s390 version, and is based on the backport in
SUSE SLES/openSUSE 4.12-based kernels.

The remaining architectures with own gup.c are sparc, mips, sh. It's unlikely
the known overflow scenario based on FUSE, which needs 140GB of RAM, is a
problem for those architectures, and I don't feel confident enough to patch
them.

Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent d00bd54f

arch/s390/mm/gup.c

+6 −3
Original line number Diff line number Diff line
@@ -39,7 +39,8 @@ static inline int gup_pte_range(pmd_t *pmdp, pmd_t pmd, unsigned long addr, 
		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));

		page = pte_page(pte);

		head = compound_head(page);

		if (!page_cache_get_speculative(head))

		if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)

		    || !page_cache_get_speculative(head)))

			return 0;

		if (unlikely(pte_val(pte) != pte_val(*ptep))) {

			put_page(head);
@@ -77,7 +78,8 @@ static inline int gup_huge_pmd(pmd_t *pmdp, pmd_t pmd, unsigned long addr, 
		refs++;

	} while (addr += PAGE_SIZE, addr != end);



	if (!page_cache_add_speculative(head, refs)) {

	if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)

	    || !page_cache_add_speculative(head, refs))) {

		*nr -= refs;

		return 0;

	}
@@ -151,7 +153,8 @@ static int gup_huge_pud(pud_t *pudp, pud_t pud, unsigned long addr, 
		refs++;

	} while (addr += PAGE_SIZE, addr != end);



	if (!page_cache_add_speculative(head, refs)) {

	if (unlikely(WARN_ON_ONCE(page_ref_count(head) < 0)

	    || !page_cache_add_speculative(head, refs))) {

		*nr -= refs;

		return 0;

	}