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| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2023-08-03 18:16:09 +0300 |
|---|---|---|
| committer | Dave Hansen <dave.hansen@linux.intel.com> | 2023-08-09 13:38:48 -0700 |
| commit | 1b8b1aa90c9c0e825b181b98b8d9e249dc395470 (patch) | |
| tree | ffbdd41fbdb3193e18ce955021539f4fbd48bd27 | |
| parent | 7324f74d39531262b8e362f228b46512e6bee632 (diff) | |
| download | linux-1b8b1aa90c9c0e825b181b98b8d9e249dc395470.tar.gz | |
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.intel.com
| -rw-r--r-- | arch/x86/entry/vdso/vma.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c index 11a5c68d121854..7645730dc228f9 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) { |