diff mbox series

[v15,07/17] mm, arm64: untag user pointers in mm/gup.c

Message ID d234cd71774f35229bdfc0a793c34d6712b73093.1557160186.git.andreyknvl@google.com (mailing list archive)
State New, archived
Headers show
Series arm64: untag user pointers passed to the kernel | expand

Commit Message

Andrey Konovalov May 6, 2019, 4:30 p.m. UTC 
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.

mm/gup.c provides a kernel interface that accepts user addresses and
manipulates user pages directly (for example get_user_pages, that is used
by the futex syscall). Since a user can provided tagged addresses, we need
to handle this case.

Add untagging to gup.c functions that use user addresses for vma lookups.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
 mm/gup.c | 4 ++++
 1 file changed, 4 insertions(+)

Comments

Catalin Marinas May 22, 2019, 11:56 a.m. UTC | #1 
On Mon, May 06, 2019 at 06:30:53PM +0200, 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.
> 
> mm/gup.c provides a kernel interface that accepts user addresses and
> manipulates user pages directly (for example get_user_pages, that is used
> by the futex syscall). Since a user can provided tagged addresses, we need
> to handle this case.
> 
> Add untagging to gup.c functions that use user addresses for vma lookups.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
diff mbox series

Patch

diff --git a/mm/gup.c b/mm/gup.c
index 91819b8ad9cc..2f477a0a7180 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -696,6 +696,8 @@  static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 	if (!nr_pages)
 		return 0;
 
+	start = untagged_addr(start);
+
 	VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
 
 	/*
@@ -858,6 +860,8 @@  int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
 	struct vm_area_struct *vma;
 	vm_fault_t ret, major = 0;
 
+	address = untagged_addr(address);
+
 	if (unlocked)
 		fault_flags |= FAULT_FLAG_ALLOW_RETRY;