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    SubjectRe: [PATCH v17 04/15] mm, arm64: untag user pointers passed to memory syscalls
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    On 12/06/2019 12:43, 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: Vincenzo Frascino <vincenzo.frascino@arm.com>

    > ---
    > 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;
    > 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))
    >

    --
    Regards,
    Vincenzo

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