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

[Catalin Marinas]

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 

Reviewed-by: Catalin Marinas 

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

[Andrey Konovalov]

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 
---
 mm/gup.c | 4 
 1 file changed, 4 insertions(+)

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;
 
-- 
2.21.0.1020.gf2820cf01a-goog

___
amd-gfx mailing list
amd-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/amd-gfx