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| author |   jsg <jsg@openbsd.org> | 2020-06-22 09:42:36 +0000 |
|---|---|---|
| committer | jsg <jsg@openbsd.org> | 2020-06-22 09:42:36 +0000 |
| commit | 0e573d0c016e750eeaa45298bee58f4eb789390f (patch) | |
| tree | f21e92d2122ebe4d388595c8eb9d29ab67806cf2 | |
| parent | Prevent potencial `state_list' corruption while pppac(4) destroys pipex(4) (diff) | |
| download | wireguard-openbsd-0e573d0c016e750eeaa45298bee58f4eb789390f.tar.xz wireguard-openbsd-0e573d0c016e750eeaa45298bee58f4eb789390f.zip | |
gup: document and work around "COW can break either way" issue
From Linus Torvalds
8e45fdafdecc8436c5b6e1620c30726056e6b29c in linux 5.7.y/5.7.3
17839856fd588f4ab6b789f482ed3ffd7c403e1f in mainline linux
| -rw-r--r-- | sys/dev/pci/drm/i915/gem/i915_gem_userptr.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/sys/dev/pci/drm/i915/gem/i915_gem_userptr.c b/sys/dev/pci/drm/i915/gem/i915_gem_userptr.c index 68bb5c37b4d..3c7e6c825f4 100644 --- a/sys/dev/pci/drm/i915/gem/i915_gem_userptr.c +++ b/sys/dev/pci/drm/i915/gem/i915_gem_userptr.c @@ -600,6 +600,14 @@ static int i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj) GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN); + /* + * Using __get_user_pages_fast() with a read-only + * access is questionable. A read-only page may be + * COW-broken, and then this might end up giving + * the wrong side of the COW.. + * + * We may or may not care. + */ if (pvec) /* defer to worker if malloc fails */ pinned = __get_user_pages_fast(obj->userptr.ptr, num_pages, |