diff options
Diffstat (limited to 'target/linux/generic/pending-3.18/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch')
| -rw-r--r-- | target/linux/generic/pending-3.18/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch | 90 |
1 files changed, 0 insertions, 90 deletions
diff --git a/target/linux/generic/pending-3.18/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch b/target/linux/generic/pending-3.18/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch deleted file mode 100644 index 213f85b0a9..0000000000 --- a/target/linux/generic/pending-3.18/097-mm-remove-gup_flags-FOLL_WRITE-games-from-__get_user.patch +++ /dev/null @@ -1,90 +0,0 @@ -From e45a502bdeae5a075257c4f061d1ff4ff0821354 Mon Sep 17 00:00:00 2001 -From: Linus Torvalds <torvalds@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@linuxace.com> -Acked-by: Hugh Dickins <hughd@google.com> -Reviewed-by: Michal Hocko <mhocko@suse.com> -Cc: Andy Lutomirski <luto@kernel.org> -Cc: Kees Cook <keescook@chromium.org> -Cc: Oleg Nesterov <oleg@redhat.com> -Cc: Willy Tarreau <w@1wt.eu> -Cc: Nick Piggin <npiggin@gmail.com> -Cc: Greg Thelen <gthelen@google.com> -Cc: stable@vger.kernel.org -Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> -Signed-off-by: Sasha Levin <alexander.levin@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; - } - |