iov_iter: saner checks on copyin/copyout

* might_fault() is better checked in caller (and e.g. fault-in + kmap_atomic
codepath also needs might_fault() coverage)
* we have already done object size checks
* we have *NOT* done access_ok() recently enough; we rely upon the
iovec array having passed sanity checks back when it had been created
and not nothing having buggered it since.  However, that's very much
non-local, so we'd better recheck that.

So the thing we want does not match anything in uaccess - we need
access_ok + kasan checks + raw copy without any zeroing.  Just define
such helpers and use them here.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index b50a478f9d34d4082f30ff419c955955b929ecfa..b3b2ee8a20b54ac597046bd1dfd5c3a6d9627c46 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -130,6 +130,24 @@
        }                                                       \
 }
 
+static int copyout(void __user *to, const void *from, size_t n)
+{
+       if (access_ok(VERIFY_WRITE, to, n)) {
+               kasan_check_read(from, n);
+               n = raw_copy_to_user(to, from, n);
+       }
+       return n;
+}
+
+static int copyin(void *to, const void __user *from, size_t n)
+{
+       if (access_ok(VERIFY_READ, from, n)) {
+               kasan_check_write(to, n);
+               n = raw_copy_from_user(to, from, n);
+       }
+       return n;
+}
+
 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
                         struct iov_iter *i)
 {
@@ -144,6 +162,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
        if (unlikely(!bytes))
                return 0;
 
+       might_fault();
        wanted = bytes;
        iov = i->iov;
        skip = i->iov_offset;
@@ -155,7 +174,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
                from = kaddr + offset;
 
                /* first chunk, usually the only one */
-               left = __copy_to_user_inatomic(buf, from, copy);
+               left = copyout(buf, from, copy);
                copy -= left;
                skip += copy;
                from += copy;
@@ -165,7 +184,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
                        iov++;
                        buf = iov->iov_base;
                        copy = min(bytes, iov->iov_len);
-                       left = __copy_to_user_inatomic(buf, from, copy);
+                       left = copyout(buf, from, copy);
                        copy -= left;
                        skip = copy;
                        from += copy;
@@ -184,7 +203,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
 
        kaddr = kmap(page);
        from = kaddr + offset;
-       left = __copy_to_user(buf, from, copy);
+       left = copyout(buf, from, copy);
        copy -= left;
        skip += copy;
        from += copy;
@@ -193,7 +212,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
                iov++;
                buf = iov->iov_base;
                copy = min(bytes, iov->iov_len);
-               left = __copy_to_user(buf, from, copy);
+               left = copyout(buf, from, copy);
                copy -= left;
                skip = copy;
                from += copy;
@@ -227,6 +246,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
        if (unlikely(!bytes))
                return 0;
 
+       might_fault();
        wanted = bytes;
        iov = i->iov;
        skip = i->iov_offset;
@@ -238,7 +258,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
                to = kaddr + offset;
 
                /* first chunk, usually the only one */
-               left = __copy_from_user_inatomic(to, buf, copy);
+               left = copyin(to, buf, copy);
                copy -= left;
                skip += copy;
                to += copy;
@@ -248,7 +268,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
                        iov++;
                        buf = iov->iov_base;
                        copy = min(bytes, iov->iov_len);
-                       left = __copy_from_user_inatomic(to, buf, copy);
+                       left = copyin(to, buf, copy);
                        copy -= left;
                        skip = copy;
                        to += copy;
@@ -267,7 +287,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
 
        kaddr = kmap(page);
        to = kaddr + offset;
-       left = __copy_from_user(to, buf, copy);
+       left = copyin(to, buf, copy);
        copy -= left;
        skip += copy;
        to += copy;
@@ -276,7 +296,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
                iov++;
                buf = iov->iov_base;
                copy = min(bytes, iov->iov_len);
-               left = __copy_from_user(to, buf, copy);
+               left = copyin(to, buf, copy);
                copy -= left;
                skip = copy;
                to += copy;
@@ -540,9 +560,10 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
        const char *from = addr;
        if (unlikely(i->type & ITER_PIPE))
                return copy_pipe_to_iter(addr, bytes, i);
+       if (iter_is_iovec(i))
+               might_fault();
        iterate_and_advance(i, bytes, v,
-               __copy_to_user(v.iov_base, (from += v.iov_len) - v.iov_len,
-                              v.iov_len),
+               copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
                memcpy_to_page(v.bv_page, v.bv_offset,
                               (from += v.bv_len) - v.bv_len, v.bv_len),
                memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
@@ -559,9 +580,10 @@ size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
                WARN_ON(1);
                return 0;
        }
+       if (iter_is_iovec(i))
+               might_fault();
        iterate_and_advance(i, bytes, v,
-               __copy_from_user((to += v.iov_len) - v.iov_len, v.iov_base,
-                                v.iov_len),
+               copyin((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
                memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
                                 v.bv_offset, v.bv_len),
                memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
@@ -581,8 +603,10 @@ bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
        if (unlikely(i->count < bytes))
                return false;
 
+       if (iter_is_iovec(i))
+               might_fault();
        iterate_all_kinds(i, bytes, v, ({
-               if (__copy_from_user((to += v.iov_len) - v.iov_len,
+               if (copyin((to += v.iov_len) - v.iov_len,
                                      v.iov_base, v.iov_len))
                        return false;
                0;}),
@@ -713,7 +737,7 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
        if (unlikely(i->type & ITER_PIPE))
                return pipe_zero(bytes, i);
        iterate_and_advance(i, bytes, v,
-               __clear_user(v.iov_base, v.iov_len),
+               clear_user(v.iov_base, v.iov_len),
                memzero_page(v.bv_page, v.bv_offset, v.bv_len),
                memset(v.iov_base, 0, v.iov_len)
        )
@@ -736,8 +760,7 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
                return 0;
        }
        iterate_all_kinds(i, bytes, v,
-               __copy_from_user_inatomic((p += v.iov_len) - v.iov_len,
-                                         v.iov_base, v.iov_len),
+               copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
                memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
                                 v.bv_offset, v.bv_len),
                memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)