From: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
commit 1b8b1aa90c9c0e825b181b98b8d9e249dc395470 upstream.
Yingcong has noticed that on the 5-level paging machine, VDSO and VVAR
VMAs are placed above the 47-bit border:
8000001a9000-8000001ad000 r--p 00000000 00:00 0 [vvar]
8000001ad000-8000001af000 r-xp 00000000 00:00 0 [vdso]
This might confuse users who are not aware of 5-level paging and expect
all userspace addresses to be under the 47-bit border.
So far problem has only been triggered with ASLR disabled, although it
may also occur with ASLR enabled if the layout is randomized in a just
right way.
The problem happens due to custom placement for the VMAs in the VDSO
code: vdso_addr() tries to place them above the stack and checks the
result against TASK_SIZE_MAX, which is wrong. TASK_SIZE_MAX is set to
the 56-bit border on 5-level paging machines. Use DEFAULT_MAP_WINDOW
instead.
Fixes: b569bab78d8d ("x86/mm: Prepare to expose larger address space to userspace")
Reported-by: Yingcong Wu <yingcong.wu@xxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/20230803151609.22141-1-kirill.shutemov%40linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/entry/vdso/vma.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -299,8 +299,8 @@ static unsigned long vdso_addr(unsigned
/* Round the lowest possible end address up to a PMD boundary. */
end = (start + len + PMD_SIZE - 1) & PMD_MASK;
- if (end >= TASK_SIZE_MAX)
- end = TASK_SIZE_MAX;
+ if (end >= DEFAULT_MAP_WINDOW)
+ end = DEFAULT_MAP_WINDOW;
end -= len;
if (end > start) {
