4.4-stable review patch. If anyone has any objections, please let me know.
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From: Lorenzo Stoakes lstoakes@gmail.com
commit d4944b0ecec0af882483fe44b66729316e575208 upstream.
This removes the redundant 'write' and 'force' parameters from __get_user_pages_unlocked() to make the use of FOLL_FORCE explicit in callers as use of this flag can result in surprising behaviour (and hence bugs) within the mm subsystem.
Signed-off-by: Lorenzo Stoakes lstoakes@gmail.com Acked-by: Paolo Bonzini pbonzini@redhat.com Reviewed-by: Jan Kara jack@suse.cz Acked-by: Michal Hocko mhocko@suse.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org [bwh: Backported to 4.4: - Defer changes in process_vm_rw_single_vec() and async_pf_execute() since they use get_user_pages_unlocked() here - Adjust context] Signed-off-by: Ben Hutchings ben.hutchings@codethink.co.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/linux/mm.h | 3 +-- mm/gup.c | 19 ++++++++++--------- mm/nommu.c | 14 ++++++++++---- virt/kvm/kvm_main.c | 11 ++++++++--- 4 files changed, 29 insertions(+), 18 deletions(-)
--- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1207,8 +1207,7 @@ long get_user_pages_locked(struct task_s int *locked); long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, unsigned long nr_pages, - int write, int force, struct page **pages, - unsigned int gup_flags); + struct page **pages, unsigned int gup_flags); long get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, unsigned long nr_pages, int write, int force, struct page **pages); --- a/mm/gup.c +++ b/mm/gup.c @@ -764,17 +764,11 @@ EXPORT_SYMBOL(get_user_pages_locked); */ __always_inline long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, unsigned long nr_pages, - int write, int force, struct page **pages, - unsigned int gup_flags) + struct page **pages, unsigned int gup_flags) { long ret; int locked = 1;
- if (write) - gup_flags |= FOLL_WRITE; - if (force) - gup_flags |= FOLL_FORCE; - down_read(&mm->mmap_sem); ret = __get_user_pages_locked(tsk, mm, start, nr_pages, pages, NULL, &locked, false, gup_flags); @@ -805,8 +799,15 @@ long get_user_pages_unlocked(struct task unsigned long start, unsigned long nr_pages, int write, int force, struct page **pages) { - return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write, - force, pages, FOLL_TOUCH); + unsigned int flags = FOLL_TOUCH; + + if (write) + flags |= FOLL_WRITE; + if (force) + flags |= FOLL_FORCE; + + return __get_user_pages_unlocked(tsk, mm, start, nr_pages, + pages, flags); } EXPORT_SYMBOL(get_user_pages_unlocked);
--- a/mm/nommu.c +++ b/mm/nommu.c @@ -211,8 +211,7 @@ EXPORT_SYMBOL(get_user_pages_locked);
long __get_user_pages_unlocked(struct task_struct *tsk, struct mm_struct *mm, unsigned long start, unsigned long nr_pages, - int write, int force, struct page **pages, - unsigned int gup_flags) + struct page **pages, unsigned int gup_flags) { long ret; down_read(&mm->mmap_sem); @@ -227,8 +226,15 @@ long get_user_pages_unlocked(struct task unsigned long start, unsigned long nr_pages, int write, int force, struct page **pages) { - return __get_user_pages_unlocked(tsk, mm, start, nr_pages, write, - force, pages, 0); + unsigned int flags = 0; + + if (write) + flags |= FOLL_WRITE; + if (force) + flags |= FOLL_FORCE; + + return __get_user_pages_unlocked(tsk, mm, start, nr_pages, + pages, flags); } EXPORT_SYMBOL(get_user_pages_unlocked);
--- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1352,10 +1352,15 @@ static int hva_to_pfn_slow(unsigned long npages = get_user_page_nowait(current, current->mm, addr, write_fault, page); up_read(¤t->mm->mmap_sem); - } else + } else { + unsigned int flags = FOLL_TOUCH | FOLL_HWPOISON; + + if (write_fault) + flags |= FOLL_WRITE; + npages = __get_user_pages_unlocked(current, current->mm, addr, 1, - write_fault, 0, page, - FOLL_TOUCH|FOLL_HWPOISON); + page, flags); + } if (npages != 1) return npages;