From 839b657a61657b8172349a303f2baee7aca66273 Mon Sep 17 00:00:00 2001 From: Stijn Tintel Date: Mon, 24 Oct 2016 05:08:07 +0300 Subject: 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 --- ...up_flags-FOLL_WRITE-games-from-__get_user.patch | 90 ++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 target/linux/generic/patches-4.1/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch (limited to 'target/linux/generic/patches-4.1') 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 0000000000..4800ee2ea2 --- /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 +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 +Acked-by: Hugh Dickins +Reviewed-by: Michal Hocko +Cc: Andy Lutomirski +Cc: Kees Cook +Cc: Oleg Nesterov +Cc: Willy Tarreau +Cc: Nick Piggin +Cc: Greg Thelen +Cc: stable@vger.kernel.org +Signed-off-by: Linus Torvalds +Signed-off-by: Sasha Levin +--- + 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; + } + -- cgit v1.2.3