From 372381ce850e3afb4108218fd7e77de851a1a420 Mon Sep 17 00:00:00 2001 From: Sona Sarmadi Date: Mon, 24 Oct 2016 10:54:37 +0200 Subject: kernel: CVE-2016-5195 Fixes privilege escalation via MAP_PRIVATE COW breakage. References: =========== https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2016-5195 http://www.securityfocus.com/bid/93793 Signed-off-by: Sona Sarmadi Signed-off-by: Adrian Dudau --- recipes-kernel/linux/files/CVE-2016-5195.patch | 100 +++++++++++++++++++++++++ recipes-kernel/linux/linux-qoriq_3.12.bbappend | 1 + 2 files changed, 101 insertions(+) create mode 100644 recipes-kernel/linux/files/CVE-2016-5195.patch diff --git a/recipes-kernel/linux/files/CVE-2016-5195.patch b/recipes-kernel/linux/files/CVE-2016-5195.patch new file mode 100644 index 0000000..bba2d0e --- /dev/null +++ b/recipes-kernel/linux/files/CVE-2016-5195.patch @@ -0,0 +1,100 @@ +From f949fcd7414197b8e04b07c480d36bc39332ff7b Mon Sep 17 00:00:00 2001 +From: Linus Torvalds +Date: Thu, 13 Oct 2016 13:07:36 -0700 +Subject: mm: remove gup_flags FOLL_WRITE games from __get_user_pages() + +commit 19be0eaffa3ac7d8eb6784ad9bdbc7d67ed8e619 upstream. + +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. + +Upstream-Status: Backport +CVE: CVE-2016-5195 + +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 +Signed-off-by: Linus Torvalds +Signed-off-by: Jiri Slaby +Signed-off-by: Sona Sarmadi +--- + include/linux/mm.h | 1 + + mm/memory.c | 14 ++++++++++++-- + 2 files changed, 13 insertions(+), 2 deletions(-) + +diff --git a/include/linux/mm.h b/include/linux/mm.h +index 79aa518..5676a67 100644 +--- a/include/linux/mm.h ++++ b/include/linux/mm.h +@@ -1749,6 +1749,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma, + #define FOLL_HWPOISON 0x100 /* check page is hwpoisoned */ + #define FOLL_NUMA 0x200 /* force NUMA hinting page fault */ + #define FOLL_MIGRATION 0x400 /* wait for page to replace migration entry */ ++#define FOLL_COW 0x4000 /* internal GUP flag */ + + typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr, + void *data); +diff --git a/mm/memory.c b/mm/memory.c +index 6192635..a0c9c6c 100644 +--- a/mm/memory.c ++++ b/mm/memory.c +@@ -1441,6 +1441,16 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address, + } + EXPORT_SYMBOL_GPL(zap_vma_ptes); + ++/* ++ * 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)); ++} ++ + /** + * follow_page_mask - look up a page descriptor from a user-virtual address + * @vma: vm_area_struct mapping @address +@@ -1550,7 +1560,7 @@ split_fallthrough: + } + 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)) + goto unlock; + + page = vm_normal_page(vma, address, pte); +@@ -1858,7 +1868,7 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, + */ + if ((ret & VM_FAULT_WRITE) && + !(vma->vm_flags & VM_WRITE)) +- foll_flags &= ~FOLL_WRITE; ++ foll_flags |= FOLL_COW; + + cond_resched(); + } +-- +cgit v0.12 + diff --git a/recipes-kernel/linux/linux-qoriq_3.12.bbappend b/recipes-kernel/linux/linux-qoriq_3.12.bbappend index b06423d..bf0eee2 100644 --- a/recipes-kernel/linux/linux-qoriq_3.12.bbappend +++ b/recipes-kernel/linux/linux-qoriq_3.12.bbappend @@ -7,5 +7,6 @@ SRC_URI += "file://ppp-CVE-2015-8569.patch \ file://net-CVE-2016-2070.patch \ file://net-CVE-2016-5696.patch \ file://CVE-2016-3136.patch \ + file://CVE-2016-5195.patch \ " -- cgit v1.2.3-54-g00ecf