From: Kirill A. Shutemov kirill.shutemov@linux.intel.com
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@intel.com Signed-off-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Signed-off-by: Dave Hansen dave.hansen@linux.intel.com Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20230803151609.22141-1-kirill.shutemov%40linux.i... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 @@ -222,8 +222,8 @@ 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) {