Re: [PATCH v17 04/15] mm, arm64: untag user pointers passed to memory syscalls

[Andrey Konovalov <andreyknvl@google.com>]

On Wed, Jun 19, 2019 at 6:46 PM Khalid Aziz <khalid.aziz@oracle.com> wrote:
>
> On 6/19/19 9:55 AM, Khalid Aziz wrote:
> > On 6/12/19 5:43 AM, Andrey Konovalov wrote:
> >> This patch is a part of a series that extends arm64 kernel ABI to allow to
> >> pass tagged user pointers (with the top byte set to something else other
> >> than 0x00) as syscall arguments.
> >>
> >> This patch allows tagged pointers to be passed to the following memory
> >> syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect,
> >> mremap, msync, munlock, move_pages.
> >>
> >> The mmap and mremap syscalls do not currently accept tagged addresses.
> >> Architectures may interpret the tag as a background colour for the
> >> corresponding vma.
> >>
> >> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
> >> Reviewed-by: Kees Cook <keescook@chromium.org>
> >> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> >> ---
> >
> > Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
> >
> >
>
> I would also recommend updating commit log for all the patches in this
> series that are changing files under mm/ as opposed to arch/arm64 to not
> reference arm64 kernel ABI since the change applies to every
> architecture. So something along the lines of "This patch is part of a
> series that extends kernel ABI to allow......."

Sure, will do in v18, thanks!

>
> --
> Khalid
>
>
> >>  mm/madvise.c   | 2 ++
> >>  mm/mempolicy.c | 3 +++
> >>  mm/migrate.c   | 2 +-
> >>  mm/mincore.c   | 2 ++
> >>  mm/mlock.c     | 4 ++++
> >>  mm/mprotect.c  | 2 ++
> >>  mm/mremap.c    | 7 +++++++
> >>  mm/msync.c     | 2 ++
> >>  8 files changed, 23 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/mm/madvise.c b/mm/madvise.c
> >> index 628022e674a7..39b82f8a698f 100644
> >> --- a/mm/madvise.c
> >> +++ b/mm/madvise.c
> >> @@ -810,6 +810,8 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
> >>      size_t len;
> >>      struct blk_plug plug;
> >>
> >> +    start = untagged_addr(start);
> >> +
> >>      if (!madvise_behavior_valid(behavior))
> >>              return error;
> >>
> >> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> >> index 01600d80ae01..78e0a88b2680 100644
> >> --- a/mm/mempolicy.c
> >> +++ b/mm/mempolicy.c
> >> @@ -1360,6 +1360,7 @@ static long kernel_mbind(unsigned long start, unsigned long len,
> >>      int err;
> >>      unsigned short mode_flags;
> >>
> >> +    start = untagged_addr(start);
> >>      mode_flags = mode & MPOL_MODE_FLAGS;
> >>      mode &= ~MPOL_MODE_FLAGS;
> >>      if (mode >= MPOL_MAX)
> >> @@ -1517,6 +1518,8 @@ static int kernel_get_mempolicy(int __user *policy,
> >>      int uninitialized_var(pval);
> >>      nodemask_t nodes;
> >>
> >> +    addr = untagged_addr(addr);
> >> +
> >>      if (nmask != NULL && maxnode < nr_node_ids)
> >>              return -EINVAL;
> >>
> >> diff --git a/mm/migrate.c b/mm/migrate.c
> >> index f2ecc2855a12..d22c45cf36b2 100644
> >> --- a/mm/migrate.c
> >> +++ b/mm/migrate.c
> >> @@ -1616,7 +1616,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
> >>                      goto out_flush;
> >>              if (get_user(node, nodes + i))
> >>                      goto out_flush;
> >> -            addr = (unsigned long)p;
> >> +            addr = (unsigned long)untagged_addr(p);
> >>
> >>              err = -ENODEV;
> >>              if (node < 0 || node >= MAX_NUMNODES)
> >> diff --git a/mm/mincore.c b/mm/mincore.c
> >> index c3f058bd0faf..64c322ed845c 100644
> >> --- a/mm/mincore.c
> >> +++ b/mm/mincore.c
> >> @@ -249,6 +249,8 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
> >>      unsigned long pages;
> >>      unsigned char *tmp;
> >>
> >> +    start = untagged_addr(start);
> >> +
> >>      /* Check the start address: needs to be page-aligned.. */
> >>      if (start & ~PAGE_MASK)
> >>              return -EINVAL;fixup_user_fault
> >> diff --git a/mm/mlock.c b/mm/mlock.c
> >> index 080f3b36415b..e82609eaa428 100644
> >> --- a/mm/mlock.c
> >> +++ b/mm/mlock.c
> >> @@ -674,6 +674,8 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
> >>      unsigned long lock_limit;
> >>      int error = -ENOMEM;
> >>
> >> +    start = untagged_addr(start);
> >> +
> >>      if (!can_do_mlock())
> >>              return -EPERM;
> >>
> >> @@ -735,6 +737,8 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
> >>  {
> >>      int ret;
> >>
> >> +    start = untagged_addr(start);
> >> +
> >>      len = PAGE_ALIGN(len + (offset_in_page(start)));
> >>      start &= PAGE_MASK;
> >>
> >> diff --git a/mm/mprotect.c b/mm/mprotect.c
> >> index bf38dfbbb4b4..19f981b733bc 100644
> >> --- a/mm/mprotect.c
> >> +++ b/mm/mprotect.c
> >> @@ -465,6 +465,8 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
> >>      const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
> >>                              (prot & PROT_READ);
> >>
> >> +    start = untagged_addr(start);
> >> +
> >>      prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
> >>      if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
> >>              return -EINVAL;
> >> diff --git a/mm/mremap.c b/mm/mremap.c
> >> index fc241d23cd97..64c9a3b8be0a 100644
> >> --- a/mm/mremap.c
> >> +++ b/mm/mremap.c
> >> @@ -606,6 +606,13 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
> >>      LIST_HEAD(uf_unmap_early);
> >>      LIST_HEAD(uf_unmap);
> >>
> >> +    /*
> >> +     * Architectures may interpret the tag passed to mmap as a background
> >> +     * colour for the corresponding vma. For mremap we don't allow tagged
> >> +     * new_addr to preserve similar behaviour to mmap.
> >> +     */
> >> +    addr = untagged_addr(addr);
> >> +
> >>      if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
> >>              return ret;
> >>
> >> diff --git a/mm/msync.c b/mm/msync.c
> >> index ef30a429623a..c3bd3e75f687 100644
> >> --- a/mm/msync.c
> >> +++ b/mm/msync.c
> >> @@ -37,6 +37,8 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
> >>      int unmapped_error = 0;
> >>      int error = -EINVAL;
> >>
> >> +    start = untagged_addr(start);
> >> +
> >>      if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
> >>              goto out;
> >>      if (offset_in_page(start))
> >>
> >
> >
>
>

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