lkml.org 
[lkml]   [2019]   [Dec]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.19 263/321] mm, gup: add missing refcount overflow checks on s390
Date
From: Vlastimil Babka <vbabka@suse.cz>

The mainline commit 8fde12ca79af ("mm: prevent get_user_pages() from
overflowing page refcount") was backported to 4.19.y stable as commit
d972ebbf42ba. 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: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/s390/mm/gup.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/s390/mm/gup.c b/arch/s390/mm/gup.c
index 2809d11c7a283..9b5b866d8adf1 100644
--- a/arch/s390/mm/gup.c
+++ b/arch/s390/mm/gup.c
@@ -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;
}
--
2.20.1


\
 
 \ /
  Last update: 2019-12-03 23:57    [W:0.726 / U:0.848 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site