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Date: Fri, 2 Oct 2020 15:52:09 -0700
From: Peter Collingbourne <pcc@...gle.com>
To: "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
Cc: x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-doc@...r.kernel.org, linux-mm@...ck.org,
linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
Arnd Bergmann <arnd@...db.de>,
Andy Lutomirski <luto@...nel.org>,
Balbir Singh <bsingharora@...il.com>,
Borislav Petkov <bp@...en8.de>,
Cyrill Gorcunov <gorcunov@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Eugene Syromiatnikov <esyr@...hat.com>,
Florian Weimer <fweimer@...hat.com>,
"H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>,
Mike Kravetz <mike.kravetz@...cle.com>,
Nadav Amit <nadav.amit@...il.com>,
Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
Peter Zijlstra <peterz@...radead.org>,
Randy Dunlap <rdunlap@...radead.org>,
"Ravi V. Shankar" <ravi.v.shankar@...el.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
Dave Martin <Dave.Martin@....com>,
Weijiang Yang <weijiang.yang@...el.com>,
Pengfei Xu <pengfei.xu@...el.com>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v13 19/26] mm: Re-introduce do_mmap_pgoff()
On Fri, Oct 2, 2020 at 8:58 AM Yu, Yu-cheng <yu-cheng.yu@...el.com> wrote:
>
> On 10/1/2020 7:06 PM, Peter Collingbourne wrote:
> > On Fri, Sep 25, 2020 at 7:57 AM Yu-cheng Yu <yu-cheng.yu@...el.com> wrote:
> >>
> >> 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 the vm_flags and do_mmap_pgoff().
> >
> > I would prefer to change the callers to pass the additional 0 argument
> > instead of bringing the wrapper function back, but if we're going to
> > bring it back then we should fix the naming (both functions take a
> > pgoff argument, so the previous name do_mmap_pgoff() was just plain
> > confusing).
> >
> > Peter
> >
>
> Thanks for your feedback. Here is the updated patch. I will re-send
> the whole series later.
>
> Yu-cheng
>
> ======
>
> From 6a9f1e6bcdb6e599a44d5f58cf4cebd28c4634a2 Mon Sep 17 00:00:00 2001
> From: Yu-cheng Yu <yu-cheng.yu@...el.com>
> Date: Wed, 12 Aug 2020 14:01:58 -0700
> Subject: [PATCH 19/26] mm: Re-introduce do_mmap_pgoff()
The subject line of the commit message needs to be updated, but aside from that:
Reviewed-by: Peter Collingbourne <pcc@...gle.com>
Peter
>
> 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, fix all callers of the wrapper by passing a zero
> vm_flags to do_mmap().
>
> Signed-off-by: Yu-cheng Yu <yu-cheng.yu@...el.com>
> Cc: Peter Collingbourne <pcc@...gle.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: linux-mm@...ck.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 d5ec30385566..ca8c11665eea 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -527,7 +527,7 @@ 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 e09d13699bbe..e020eea33138 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2560,7 +2560,8 @@ 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 e25c7c6106bc..91474258933d 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 574b3f273462..fc04184d2eae 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1365,11 +1365,11 @@ 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;
> @@ -1431,7 +1431,7 @@ 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)
> @@ -3007,7 +3007,7 @@ 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 75a327149af1..f67d6bcdfc9f 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -1078,6 +1078,7 @@ 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)
> @@ -1085,7 +1086,6 @@ 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;
>
> @@ -1104,7 +1104,7 @@ 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 5ef378a2a038..beb8b881c080 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -503,7 +503,7 @@ 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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