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Howlett" , Vlastimil Babka , Harry Yoo , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C0AB74000C X-Stat-Signature: d61y1fznfyy6y3aeo4maokfxa555otro X-HE-Tag: 1753457268-198584 X-HE-Meta: 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 5Ly9FWDm V7JUbPCjYQY/ur+bIfP7VtjmQ8g12jAx/6YuYt0Y7nTIrGxFLej0CrmAOkehW00MTuUxU767UQy9NtHkFZzOc0Ycv5+C4dTUMK+bOcv++nLe7vsdKUWnHde245E8mMHXqJx9xYeFnqSdd+t+GKgXC2qWmfgMfTzU1+GjjJYA7kzj19VZn2LclbDaRqbwGK5VsxCdrmOAOy8jaDRX29TXq8iJM0Hr/BF18Q5BZ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jul 25, 2025 at 5:22=E2=80=AFPM Lorenzo Stoakes wrote: > On Fri, Jul 25, 2025 at 05:15:45PM +0200, Jann Horn wrote: > > On Fri, Jul 25, 2025 at 5:07=E2=80=AFPM Lorenzo Stoakes > > wrote: > > Basically CONFIG_SLUB_RCU_DEBUG turns kmem_cache_free() on > > SLAB_TYPESAFE_BY_RCU slabs into something like kfree_rcu(), and this > > allows KASAN to catch UAF access. > > > > > It's surely only UAF? > > > > I mean, "UAF" is kind of vague when talking about SLAB_TYPESAFE_BY_RCU > > slabs. I am only using the term "UAF" when talking about a situation > > where accessing the anon_vma object is entirely forbidden because an > > RCU grace period has passed after it was "freed" with > > kmem_cache_free(). > > Could it not be either case? Or are we sure it's been accessed within tha= t grace > period? If there is a bug here, it could be either case. The check covers both cases in CONFIG_SLUB_RCU_DEBUG builds (as long as the object hasn't already moved all the way through the KASAN quarantine, the usual KASAN caveat). Note that atomic_read() implicitly causes KASAN to check that the object is still accessible.