[source] kernel: add fix for CVE-2016-5195
LEDE Commits
lede-commits at lists.infradead.org
Mon Oct 24 10:49:23 PDT 2016
stintel pushed a commit to source.git, branch master:
https://git.lede-project.org/839b657a61657b8172349a303f2baee7aca66273
commit 839b657a61657b8172349a303f2baee7aca66273
Author: Stijn Tintel <stijn at linux-ipv6.be>
AuthorDate: Mon Oct 24 05:08:07 2016 +0300
kernel: add fix for CVE-2016-5195
Add fix for CVE-2016-5195 to kernel 3.18 and 4.1.
Kernel 4.4 is already fixed since version 4.4.26 which was committed in
32c28a78f798dffb983a7f00342b471e5e4ac177.
Patches taken from Sasha Levin's linux-stable git tree:
http://git.kernel.org/cgit/linux/kernel/git/sashal/linux-stable.git/
Signed-off-by: Stijn Tintel <stijn at linux-ipv6.be>
---
...up_flags-FOLL_WRITE-games-from-__get_user.patch | 90 ++++++++++++++++++++++
...up_flags-FOLL_WRITE-games-from-__get_user.patch | 90 ++++++++++++++++++++++
2 files changed, 180 insertions(+)
diff --git a/target/linux/generic/patches-3.18/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch b/target/linux/generic/patches-3.18/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch
new file mode 100644
index 0000000..213f85b
--- /dev/null
+++ b/target/linux/generic/patches-3.18/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch
@@ -0,0 +1,90 @@
+From e45a502bdeae5a075257c4f061d1ff4ff0821354 Mon Sep 17 00:00:00 2001
+From: Linus Torvalds <torvalds at linux-foundation.org>
+Date: Thu, 13 Oct 2016 13:07:36 -0700
+Subject: [PATCH] mm: remove gup_flags FOLL_WRITE games from __get_user_pages()
+
+[ Upstream commit 19be0eaffa3ac7d8eb6784ad9bdbc7d67ed8e619 ]
+
+This is an ancient bug that was actually attempted to be fixed once
+(badly) by me eleven years ago in commit 4ceb5db9757a ("Fix
+get_user_pages() race for write access") but that was then undone due to
+problems on s390 by commit f33ea7f404e5 ("fix get_user_pages bug").
+
+In the meantime, the s390 situation has long been fixed, and we can now
+fix it by checking the pte_dirty() bit properly (and do it better). The
+s390 dirty bit was implemented in abf09bed3cce ("s390/mm: implement
+software dirty bits") which made it into v3.9. Earlier kernels will
+have to look at the page state itself.
+
+Also, the VM has become more scalable, and what used a purely
+theoretical race back then has become easier to trigger.
+
+To fix it, we introduce a new internal FOLL_COW flag to mark the "yes,
+we already did a COW" rather than play racy games with FOLL_WRITE that
+is very fundamental, and then use the pte dirty flag to validate that
+the FOLL_COW flag is still valid.
+
+Reported-and-tested-by: Phil "not Paul" Oester <kernel at linuxace.com>
+Acked-by: Hugh Dickins <hughd at google.com>
+Reviewed-by: Michal Hocko <mhocko at suse.com>
+Cc: Andy Lutomirski <luto at kernel.org>
+Cc: Kees Cook <keescook at chromium.org>
+Cc: Oleg Nesterov <oleg at redhat.com>
+Cc: Willy Tarreau <w at 1wt.eu>
+Cc: Nick Piggin <npiggin at gmail.com>
+Cc: Greg Thelen <gthelen at google.com>
+Cc: stable at vger.kernel.org
+Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
+Signed-off-by: Sasha Levin <alexander.levin at verizon.com>
+---
+ include/linux/mm.h | 1 +
+ mm/gup.c | 14 ++++++++++++--
+ 2 files changed, 13 insertions(+), 2 deletions(-)
+
+--- a/include/linux/mm.h
++++ b/include/linux/mm.h
+@@ -2029,6 +2029,7 @@ static inline struct page *follow_page(s
+ #define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
+ #define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
+ #define FOLL_TRIED 0x800 /* a retry, previous pass started an IO */
++#define FOLL_COW 0x4000 /* internal GUP flag */
+
+ typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
+ void *data);
+--- a/mm/gup.c
++++ b/mm/gup.c
+@@ -32,6 +32,16 @@ static struct page *no_page_table(struct
+ return NULL;
+ }
+
++/*
++ * FOLL_FORCE can write to even unwritable pte's, but only
++ * after we've gone through a COW cycle and they are dirty.
++ */
++static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
++{
++ return pte_write(pte) ||
++ ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
++}
++
+ static struct page *follow_page_pte(struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd, unsigned int flags)
+ {
+@@ -66,7 +76,7 @@ retry:
+ }
+ if ((flags & FOLL_NUMA) && pte_numa(pte))
+ goto no_page;
+- if ((flags & FOLL_WRITE) && !pte_write(pte)) {
++ if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
+ pte_unmap_unlock(ptep, ptl);
+ return NULL;
+ }
+@@ -315,7 +325,7 @@ static int faultin_page(struct task_stru
+ * reCOWed by userspace write).
+ */
+ if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
+- *flags &= ~FOLL_WRITE;
++ *flags |= FOLL_COW;
+ return 0;
+ }
+
diff --git a/target/linux/generic/patches-4.1/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch b/target/linux/generic/patches-4.1/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch
new file mode 100644
index 0000000..4800ee2
--- /dev/null
+++ b/target/linux/generic/patches-4.1/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch
@@ -0,0 +1,90 @@
+From c865f98df72112a3997b219bf711bc46c1e90706 Mon Sep 17 00:00:00 2001
+From: Linus Torvalds <torvalds at linux-foundation.org>
+Date: Thu, 13 Oct 2016 13:07:36 -0700
+Subject: [PATCH] mm: remove gup_flags FOLL_WRITE games from __get_user_pages()
+
+[ Upstream commit 19be0eaffa3ac7d8eb6784ad9bdbc7d67ed8e619 ]
+
+This is an ancient bug that was actually attempted to be fixed once
+(badly) by me eleven years ago in commit 4ceb5db9757a ("Fix
+get_user_pages() race for write access") but that was then undone due to
+problems on s390 by commit f33ea7f404e5 ("fix get_user_pages bug").
+
+In the meantime, the s390 situation has long been fixed, and we can now
+fix it by checking the pte_dirty() bit properly (and do it better). The
+s390 dirty bit was implemented in abf09bed3cce ("s390/mm: implement
+software dirty bits") which made it into v3.9. Earlier kernels will
+have to look at the page state itself.
+
+Also, the VM has become more scalable, and what used a purely
+theoretical race back then has become easier to trigger.
+
+To fix it, we introduce a new internal FOLL_COW flag to mark the "yes,
+we already did a COW" rather than play racy games with FOLL_WRITE that
+is very fundamental, and then use the pte dirty flag to validate that
+the FOLL_COW flag is still valid.
+
+Reported-and-tested-by: Phil "not Paul" Oester <kernel at linuxace.com>
+Acked-by: Hugh Dickins <hughd at google.com>
+Reviewed-by: Michal Hocko <mhocko at suse.com>
+Cc: Andy Lutomirski <luto at kernel.org>
+Cc: Kees Cook <keescook at chromium.org>
+Cc: Oleg Nesterov <oleg at redhat.com>
+Cc: Willy Tarreau <w at 1wt.eu>
+Cc: Nick Piggin <npiggin at gmail.com>
+Cc: Greg Thelen <gthelen at google.com>
+Cc: stable at vger.kernel.org
+Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
+Signed-off-by: Sasha Levin <alexander.levin at verizon.com>
+---
+ include/linux/mm.h | 1 +
+ mm/gup.c | 14 ++++++++++++--
+ 2 files changed, 13 insertions(+), 2 deletions(-)
+
+--- a/include/linux/mm.h
++++ b/include/linux/mm.h
+@@ -2064,6 +2064,7 @@ static inline struct page *follow_page(s
+ #define FOLL_NUMA 0x200 /* force NUMA hinting page fault */
+ #define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */
+ #define FOLL_TRIED 0x800 /* a retry, previous pass started an IO */
++#define FOLL_COW 0x4000 /* internal GUP flag */
+
+ typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
+ void *data);
+--- a/mm/gup.c
++++ b/mm/gup.c
+@@ -32,6 +32,16 @@ static struct page *no_page_table(struct
+ return NULL;
+ }
+
++/*
++ * FOLL_FORCE can write to even unwritable pte's, but only
++ * after we've gone through a COW cycle and they are dirty.
++ */
++static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
++{
++ return pte_write(pte) ||
++ ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
++}
++
+ static struct page *follow_page_pte(struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd, unsigned int flags)
+ {
+@@ -66,7 +76,7 @@ retry:
+ }
+ if ((flags & FOLL_NUMA) && pte_protnone(pte))
+ goto no_page;
+- if ((flags & FOLL_WRITE) && !pte_write(pte)) {
++ if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) {
+ pte_unmap_unlock(ptep, ptl);
+ return NULL;
+ }
+@@ -315,7 +325,7 @@ static int faultin_page(struct task_stru
+ * reCOWed by userspace write).
+ */
+ if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE))
+- *flags &= ~FOLL_WRITE;
++ *flags |= FOLL_COW;
+ return 0;
+ }
+
More information about the lede-commits
mailing list