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SubjectRe: [PATCH v22 21/28] mm: Re-introduce vm_flags to do_mmap()
Date
* Yu-cheng Yu <yu-cheng.yu@intel.com> [210310 17:02]:
> There was no more caller passing vm_flags to do_mmap(), and vm_flags was
> removed from the function's input by:
>
> commit 45e55300f114 ("mm: remove unnecessary wrapper function do_mmap_pgoff()").
>
> There is a new user now. Shadow stack allocation passes VM_SHSTK to
> do_mmap(). Re-introduce vm_flags to do_mmap(), but without the old wrapper
> do_mmap_pgoff(). Instead, make all callers of the wrapper pass a zero
> vm_flags to do_mmap().

In a later patch, PROT_SHSTK is introduced. do_mmap() already takes the
PROT flags. Could PROT_SHSTK be used to indicate VM_SHSTK instead of
expanding the arguments passed to do_mmap()?

>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
> Reviewed-by: Peter Collingbourne <pcc@google.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: linux-mm@kvack.org
> ---
> fs/aio.c | 2 +-
> include/linux/mm.h | 3 ++-
> ipc/shm.c | 2 +-
> mm/mmap.c | 10 +++++-----
> mm/nommu.c | 4 ++--
> mm/util.c | 2 +-
> 6 files changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 1f32da13d39e..b5d0586209a7 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -529,7 +529,7 @@ static int aio_setup_ring(struct kioctx *ctx, unsigned int nr_events)
>
> ctx->mmap_base = do_mmap(ctx->aio_ring_file, 0, ctx->mmap_size,
> PROT_READ | PROT_WRITE,
> - MAP_SHARED, 0, &unused, NULL);
> + MAP_SHARED, 0, 0, &unused, NULL);
> mmap_write_unlock(mm);
> if (IS_ERR((void *)ctx->mmap_base)) {
> ctx->mmap_size = 0;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index e363173f7634..2731889f49c1 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2543,7 +2543,8 @@ extern unsigned long mmap_region(struct file *file, unsigned long addr,
> struct list_head *uf);
> extern unsigned long do_mmap(struct file *file, unsigned long addr,
> unsigned long len, unsigned long prot, unsigned long flags,
> - unsigned long pgoff, unsigned long *populate, struct list_head *uf);
> + vm_flags_t vm_flags, unsigned long pgoff, unsigned long *populate,
> + struct list_head *uf);
> extern int __do_munmap(struct mm_struct *, unsigned long, size_t,
> struct list_head *uf, bool downgrade);
> extern int do_munmap(struct mm_struct *, unsigned long, size_t,
> diff --git a/ipc/shm.c b/ipc/shm.c
> index febd88daba8c..b6370eb1eaab 100644
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -1556,7 +1556,7 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg,
> goto invalid;
> }
>
> - addr = do_mmap(file, addr, size, prot, flags, 0, &populate, NULL);
> + addr = do_mmap(file, addr, size, prot, flags, 0, 0, &populate, NULL);
> *raddr = addr;
> err = 0;
> if (IS_ERR_VALUE(addr))
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 2ac67882ace2..99077171010b 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1401,11 +1401,11 @@ static inline bool file_mmap_ok(struct file *file, struct inode *inode,
> */
> unsigned long do_mmap(struct file *file, unsigned long addr,
> unsigned long len, unsigned long prot,
> - unsigned long flags, unsigned long pgoff,
> - unsigned long *populate, struct list_head *uf)
> + unsigned long flags, vm_flags_t vm_flags,
> + unsigned long pgoff, unsigned long *populate,
> + struct list_head *uf)
> {
> struct mm_struct *mm = current->mm;
> - vm_flags_t vm_flags;
> int pkey = 0;
>
> *populate = 0;
> @@ -1467,7 +1467,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
> * to. we assume access permissions have been handled by the open
> * of the memory object, so we don't do any here.
> */
> - vm_flags = calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
> + vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
> mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
>
> if (flags & MAP_LOCKED)
> @@ -3047,7 +3047,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
>
> file = get_file(vma->vm_file);
> ret = do_mmap(vma->vm_file, start, size,
> - prot, flags, pgoff, &populate, NULL);
> + prot, flags, 0, pgoff, &populate, NULL);
> fput(file);
> out:
> mmap_write_unlock(mm);
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 5c9ab799c0e6..9b6f7a1895c2 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -1071,6 +1071,7 @@ unsigned long do_mmap(struct file *file,
> unsigned long len,
> unsigned long prot,
> unsigned long flags,
> + vm_flags_t vm_flags,
> unsigned long pgoff,
> unsigned long *populate,
> struct list_head *uf)
> @@ -1078,7 +1079,6 @@ unsigned long do_mmap(struct file *file,
> struct vm_area_struct *vma;
> struct vm_region *region;
> struct rb_node *rb;
> - vm_flags_t vm_flags;
> unsigned long capabilities, result;
> int ret;
>
> @@ -1097,7 +1097,7 @@ unsigned long do_mmap(struct file *file,
>
> /* we've determined that we can make the mapping, now translate what we
> * now know into VMA flags */
> - vm_flags = determine_vm_flags(file, prot, flags, capabilities);
> + vm_flags |= determine_vm_flags(file, prot, flags, capabilities);
>
> /* we're going to need to record the mapping */
> region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
> diff --git a/mm/util.c b/mm/util.c
> index 54870226cea6..49cbd4400d13 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -516,7 +516,7 @@ unsigned long vm_mmap_pgoff(struct file *file, unsigned long addr,
> if (!ret) {
> if (mmap_write_lock_killable(mm))
> return -EINTR;
> - ret = do_mmap(file, addr, len, prot, flag, pgoff, &populate,
> + ret = do_mmap(file, addr, len, prot, flag, 0, pgoff, &populate,
> &uf);
> mmap_write_unlock(mm);
> userfaultfd_unmap_complete(mm, &uf);
> --
> 2.21.0
>
>
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