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| author | Abdifatah Suruur <suruurism@gmail.com> | 2026-08-13 20:47:07 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-08-18 09:14:43 -0700 |
| commit | a5edadbae57e2298a56cf7a4e774a027905a331f (patch) | |
| tree | 24199d136e5993fd9f2a5a9dc2bd5e2e33991699 | |
| parent | c0726f0caf8c6b3208552949e17d23634a2f3129 (diff) | |
| download | linux-a5edadbae57e2298a56cf7a4e774a027905a331f.tar.gz linux-a5edadbae57e2298a56cf7a4e774a027905a331f.zip | |
ptp: vmclock: prevent read-only mappings from becoming writable
vmclock_miscdev_mmap() rejects writable mappings of the shared vmclock
ABI page with -EROFS, but leaves VM_MAYWRITE set. Userspace can map the
page read-only and then upgrade it to writable with mprotect(), after
which the guest can corrupt the host-written timekeeping data (sequence
counter, UTC time, TSC offset) that the vmclock ABI defines as read-only.
Clear VM_MAYWRITE on the read-only path so the mapping cannot be
upgraded, as i915 does for its read-only objects and as fixed in drm/vc4
(CVE-2026-68445) and drm/panthor (CVE-2024-53071).
Cc: stable@vger.kernel.org
Fixes: 205032724226 ("ptp: Add support for the AMZNC10C 'vmclock' device")
Signed-off-by: Abdifatah Suruur <suruurism@gmail.com>
Link: https://patch.msgid.link/20260813174707.14809-1-suruurism@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/ptp/ptp_vmclock.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/ptp/ptp_vmclock.c b/drivers/ptp/ptp_vmclock.c index eebdcd5ebc08..bb0e14bac9f2 100644 --- a/drivers/ptp/ptp_vmclock.c +++ b/drivers/ptp/ptp_vmclock.c @@ -372,6 +372,12 @@ static int vmclock_miscdev_mmap(struct file *fp, struct vm_area_struct *vma) if ((vma->vm_flags & (VM_READ|VM_WRITE)) != VM_READ) return -EROFS; + /* + * Restrict the read-only mapping so it cannot be upgraded to + * writable later with mprotect(). + */ + vm_flags_clear(vma, VM_MAYWRITE); + if (vma->vm_end - vma->vm_start != PAGE_SIZE || vma->vm_pgoff) return -EINVAL; |