diff mbox series

[v19,08/15] userfaultfd: untag user pointers

Message ID cdc59ddd7011012ca2e689bc88c3b65b1ea7e413.1563904656.git.andreyknvl@google.com (mailing list archive)
State New
Headers show
Series arm64: untag user pointers passed to the kernel | expand

Commit Message

Andrey Konovalov July 23, 2019, 5:58 p.m. UTC 
This patch is a part of a series that extends kernel ABI to allow to pass
tagged user pointers (with the top byte set to something else other than
0x00) as syscall arguments.

userfaultfd code use provided user pointers for vma lookups, which can
only by done with untagged pointers.

Untag user pointers in validate_range().

Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 fs/userfaultfd.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)
diff mbox series

Patch

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index ccbdbd62f0d8..6284a4e719cb 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -1271,21 +1271,23 @@  static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
 }
 
 static __always_inline int validate_range(struct mm_struct *mm,
-					  __u64 start, __u64 len)
+					  __u64 *start, __u64 len)
 {
 	__u64 task_size = mm->task_size;
 
-	if (start & ~PAGE_MASK)
+	*start = untagged_addr(*start);
+
+	if (*start & ~PAGE_MASK)
 		return -EINVAL;
 	if (len & ~PAGE_MASK)
 		return -EINVAL;
 	if (!len)
 		return -EINVAL;
-	if (start < mmap_min_addr)
+	if (*start < mmap_min_addr)
 		return -EINVAL;
-	if (start >= task_size)
+	if (*start >= task_size)
 		return -EINVAL;
-	if (len > task_size - start)
+	if (len > task_size - *start)
 		return -EINVAL;
 	return 0;
 }
@@ -1335,7 +1337,7 @@  static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 		goto out;
 	}
 
-	ret = validate_range(mm, uffdio_register.range.start,
+	ret = validate_range(mm, &uffdio_register.range.start,
 			     uffdio_register.range.len);
 	if (ret)
 		goto out;
@@ -1524,7 +1526,7 @@  static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 	if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
 		goto out;
 
-	ret = validate_range(mm, uffdio_unregister.start,
+	ret = validate_range(mm, &uffdio_unregister.start,
 			     uffdio_unregister.len);
 	if (ret)
 		goto out;
@@ -1675,7 +1677,7 @@  static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
 	if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
 		goto out;
 
-	ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len);
+	ret = validate_range(ctx->mm, &uffdio_wake.start, uffdio_wake.len);
 	if (ret)
 		goto out;
 
@@ -1715,7 +1717,7 @@  static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
 			   sizeof(uffdio_copy)-sizeof(__s64)))
 		goto out;
 
-	ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
+	ret = validate_range(ctx->mm, &uffdio_copy.dst, uffdio_copy.len);
 	if (ret)
 		goto out;
 	/*
@@ -1771,7 +1773,7 @@  static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
 			   sizeof(uffdio_zeropage)-sizeof(__s64)))
 		goto out;
 
-	ret = validate_range(ctx->mm, uffdio_zeropage.range.start,
+	ret = validate_range(ctx->mm, &uffdio_zeropage.range.start,
 			     uffdio_zeropage.range.len);
 	if (ret)
 		goto out;