| Message ID | 20161013002020.3062-3-lstoakes@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 13/10/2016 02:20, Lorenzo Stoakes wrote: > This patch removes the 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> > --- > include/linux/mm.h | 3 +-- > mm/gup.c | 17 +++++++++-------- > mm/nommu.c | 12 +++++++++--- > mm/process_vm_access.c | 7 +++++-- > virt/kvm/async_pf.c | 3 ++- > virt/kvm/kvm_main.c | 11 ++++++++--- > 6 files changed, 34 insertions(+), 19 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index e9caec6..2db98b6 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1285,8 +1285,7 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages, > int write, int force, struct page **pages, 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(unsigned long start, unsigned long nr_pages, > int write, int force, struct page **pages); > int get_user_pages_fast(unsigned long start, int nr_pages, int write, > diff --git a/mm/gup.c b/mm/gup.c > index ba83942..3d620dd 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -865,17 +865,11 @@ 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); > @@ -905,8 +899,15 @@ EXPORT_SYMBOL(__get_user_pages_unlocked); > long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, > int write, int force, struct page **pages) > { > + unsigned int flags = FOLL_TOUCH; > + > + if (write) > + flags |= FOLL_WRITE; > + if (force) > + flags |= FOLL_FORCE; > + > return __get_user_pages_unlocked(current, current->mm, start, nr_pages, > - write, force, pages, FOLL_TOUCH); > + pages, flags); > } > EXPORT_SYMBOL(get_user_pages_unlocked); > > diff --git a/mm/nommu.c b/mm/nommu.c > index 95daf81..925dcc1 100644 > --- a/mm/nommu.c > +++ b/mm/nommu.c > @@ -185,8 +185,7 @@ 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); > @@ -200,8 +199,15 @@ EXPORT_SYMBOL(__get_user_pages_unlocked); > long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, > int write, int force, struct page **pages) > { > + unsigned int flags = 0; > + > + if (write) > + flags |= FOLL_WRITE; > + if (force) > + flags |= FOLL_FORCE; > + > return __get_user_pages_unlocked(current, current->mm, start, nr_pages, > - write, force, pages, 0); > + pages, flags); > } > EXPORT_SYMBOL(get_user_pages_unlocked); > > diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c > index 07514d4..be8dc8d 100644 > --- a/mm/process_vm_access.c > +++ b/mm/process_vm_access.c > @@ -88,12 +88,16 @@ static int process_vm_rw_single_vec(unsigned long addr, > ssize_t rc = 0; > unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES > / sizeof(struct pages *); > + unsigned int flags = FOLL_REMOTE; > > /* Work out address and page range required */ > if (len == 0) > return 0; > nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; > > + if (vm_write) > + flags |= FOLL_WRITE; > + > while (!rc && nr_pages && iov_iter_count(iter)) { > int pages = min(nr_pages, max_pages_per_loop); > size_t bytes; > @@ -104,8 +108,7 @@ static int process_vm_rw_single_vec(unsigned long addr, > * current/current->mm > */ > pages = __get_user_pages_unlocked(task, mm, pa, pages, > - vm_write, 0, process_pages, > - FOLL_REMOTE); > + process_pages, flags); > if (pages <= 0) > return -EFAULT; > > diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c > index db96688..8035cc1 100644 > --- a/virt/kvm/async_pf.c > +++ b/virt/kvm/async_pf.c > @@ -84,7 +84,8 @@ static void async_pf_execute(struct work_struct *work) > * mm and might be done in another context, so we must > * use FOLL_REMOTE. > */ > - __get_user_pages_unlocked(NULL, mm, addr, 1, 1, 0, NULL, FOLL_REMOTE); > + __get_user_pages_unlocked(NULL, mm, addr, 1, NULL, > + FOLL_WRITE | FOLL_REMOTE); > > kvm_async_page_present_sync(vcpu, apf); > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 81dfc73..28510e7 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1416,10 +1416,15 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault, > down_read(¤t->mm->mmap_sem); > npages = get_user_page_nowait(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; > > Acked-by: Paolo Bonzini <pbonzini@redhat.com>
On Thu 13-10-16 01:20:12, Lorenzo Stoakes wrote: > This patch removes the 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> The patch looks good. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza
diff --git a/include/linux/mm.h b/include/linux/mm.h index e9caec6..2db98b6 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1285,8 +1285,7 @@ long get_user_pages_locked(unsigned long start, unsigned long nr_pages, int write, int force, struct page **pages, 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(unsigned long start, unsigned long nr_pages, int write, int force, struct page **pages); int get_user_pages_fast(unsigned long start, int nr_pages, int write, diff --git a/mm/gup.c b/mm/gup.c index ba83942..3d620dd 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -865,17 +865,11 @@ 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); @@ -905,8 +899,15 @@ EXPORT_SYMBOL(__get_user_pages_unlocked); long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, int write, int force, struct page **pages) { + unsigned int flags = FOLL_TOUCH; + + if (write) + flags |= FOLL_WRITE; + if (force) + flags |= FOLL_FORCE; + return __get_user_pages_unlocked(current, current->mm, start, nr_pages, - write, force, pages, FOLL_TOUCH); + pages, flags); } EXPORT_SYMBOL(get_user_pages_unlocked); diff --git a/mm/nommu.c b/mm/nommu.c index 95daf81..925dcc1 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -185,8 +185,7 @@ 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); @@ -200,8 +199,15 @@ EXPORT_SYMBOL(__get_user_pages_unlocked); long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, int write, int force, struct page **pages) { + unsigned int flags = 0; + + if (write) + flags |= FOLL_WRITE; + if (force) + flags |= FOLL_FORCE; + return __get_user_pages_unlocked(current, current->mm, start, nr_pages, - write, force, pages, 0); + pages, flags); } EXPORT_SYMBOL(get_user_pages_unlocked); diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c index 07514d4..be8dc8d 100644 --- a/mm/process_vm_access.c +++ b/mm/process_vm_access.c @@ -88,12 +88,16 @@ static int process_vm_rw_single_vec(unsigned long addr, ssize_t rc = 0; unsigned long max_pages_per_loop = PVM_MAX_KMALLOC_PAGES / sizeof(struct pages *); + unsigned int flags = FOLL_REMOTE; /* Work out address and page range required */ if (len == 0) return 0; nr_pages = (addr + len - 1) / PAGE_SIZE - addr / PAGE_SIZE + 1; + if (vm_write) + flags |= FOLL_WRITE; + while (!rc && nr_pages && iov_iter_count(iter)) { int pages = min(nr_pages, max_pages_per_loop); size_t bytes; @@ -104,8 +108,7 @@ static int process_vm_rw_single_vec(unsigned long addr, * current/current->mm */ pages = __get_user_pages_unlocked(task, mm, pa, pages, - vm_write, 0, process_pages, - FOLL_REMOTE); + process_pages, flags); if (pages <= 0) return -EFAULT; diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c index db96688..8035cc1 100644 --- a/virt/kvm/async_pf.c +++ b/virt/kvm/async_pf.c @@ -84,7 +84,8 @@ static void async_pf_execute(struct work_struct *work) * mm and might be done in another context, so we must * use FOLL_REMOTE. */ - __get_user_pages_unlocked(NULL, mm, addr, 1, 1, 0, NULL, FOLL_REMOTE); + __get_user_pages_unlocked(NULL, mm, addr, 1, NULL, + FOLL_WRITE | FOLL_REMOTE); kvm_async_page_present_sync(vcpu, apf); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 81dfc73..28510e7 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1416,10 +1416,15 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault, down_read(¤t->mm->mmap_sem); npages = get_user_page_nowait(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;
This patch removes the 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> --- include/linux/mm.h | 3 +-- mm/gup.c | 17 +++++++++-------- mm/nommu.c | 12 +++++++++--- mm/process_vm_access.c | 7 +++++-- virt/kvm/async_pf.c | 3 ++- virt/kvm/kvm_main.c | 11 ++++++++--- 6 files changed, 34 insertions(+), 19 deletions(-)