The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: 1b8b1aa90c9c0e825b181b98b8d9e249dc395470 Gitweb: https://git.kernel.org/tip/1b8b1aa90c9c0e825b181b98b8d9e249dc395470 Author: Kirill A. Shutemov kirill.shutemov@linux.intel.com AuthorDate: Thu, 03 Aug 2023 18:16:09 +03:00 Committer: Dave Hansen dave.hansen@linux.intel.com CommitterDate: Wed, 09 Aug 2023 13:38:48 -07:00

x86/mm: Fix VDSO and VVAR placement on 5-level paging machines

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... --- arch/x86/entry/vdso/vma.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 11a5c68..7645730 100644 --- a/arch/x86/entry/vdso/vma.c +++ b/arch/x86/entry/vdso/vma.c @@ -299,8 +299,8 @@ static unsigned long vdso_addr(unsigned long start, unsigned len)

/* 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) {