mm: userfaultfd: check for start + len overflow in validate_range

Most userfaultfd ioctls take a `start + len` range as an argument.  We
have the validate_range helper to check that such ranges are valid.
However, some (but not all!) ioctls *also* check that `start + len`
doesn't wrap around (overflow).

Just check for this in validate_range.  This saves some repetitive code,
and adds the check to some ioctls which weren't bothering to check for it
before.

[axelrasmussen@google.com: call validate_range() on the src range too]
Link: https://lkml.kernel.org/r/20230714182932.2608735-1-axelrasmussen@google.com
[axelrasmussen@google.com: fix src/dst validation]
Link: https://lkml.kernel.org/r/20230810192128.1855570-1-axelrasmussen@google.com
Link: https://lkml.kernel.org/r/20230707215540.2324998-3-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Gaosheng Cui <cuigaosheng1@huawei.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nadav Amit <namit@vmware.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suleiman Souhlal <suleiman@google.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: T.J. Alumbaugh <talumbau@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: ZhangPeng <zhangpeng362@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index ae711f1..c2ed7dc 100644 (file)
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1289,13 +1289,11 @@ static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
                __wake_userfault(ctx, range);
 }
 
-static __always_inline int validate_range(struct mm_struct *mm,
-                                         __u64 start, __u64 len)
+static __always_inline int validate_unaligned_range(
+       struct mm_struct *mm, __u64 start, __u64 len)
 {
        __u64 task_size = mm->task_size;
 
-       if (start & ~PAGE_MASK)
-               return -EINVAL;
        if (len & ~PAGE_MASK)
                return -EINVAL;
        if (!len)
@@ -1306,9 +1304,20 @@ static __always_inline int validate_range(struct mm_struct *mm,
                return -EINVAL;
        if (len > task_size - start)
                return -EINVAL;
+       if (start + len <= start)
+               return -EINVAL;
        return 0;
 }
 
+static __always_inline int validate_range(struct mm_struct *mm,
+                                         __u64 start, __u64 len)
+{
+       if (start & ~PAGE_MASK)
+               return -EINVAL;
+
+       return validate_unaligned_range(mm, start, len);
+}
+
 static int userfaultfd_register(struct userfaultfd_ctx *ctx,
                                unsigned long arg)
 {
@@ -1757,17 +1766,15 @@ static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
                           sizeof(uffdio_copy)-sizeof(__s64)))
                goto out;
 
+       ret = validate_unaligned_range(ctx->mm, uffdio_copy.src,
+                                      uffdio_copy.len);
+       if (ret)
+               goto out;
        ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
        if (ret)
                goto out;
-       /*
-        * double check for wraparound just in case. copy_from_user()
-        * will later check uffdio_copy.src + uffdio_copy.len to fit
-        * in the userland range.
-        */
+
        ret = -EINVAL;
-       if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src)
-               goto out;
        if (uffdio_copy.mode & ~(UFFDIO_COPY_MODE_DONTWAKE|UFFDIO_COPY_MODE_WP))
                goto out;
        if (uffdio_copy.mode & UFFDIO_COPY_MODE_WP)
@@ -1927,11 +1934,6 @@ static int userfaultfd_continue(struct userfaultfd_ctx *ctx, unsigned long arg)
                goto out;
 
        ret = -EINVAL;
-       /* double check for wraparound just in case. */
-       if (uffdio_continue.range.start + uffdio_continue.range.len <=
-           uffdio_continue.range.start) {
-               goto out;
-       }
        if (uffdio_continue.mode & ~(UFFDIO_CONTINUE_MODE_DONTWAKE |
                                     UFFDIO_CONTINUE_MODE_WP))
                goto out;