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Howlett" , Lorenzo Stoakes , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5] mm/userfaultfd: detect VMA type change after copy retry in mfill_copy_folio_retry() Message-Id: <20260409101451.66dcee85281b84f00c645ecb@linux-foundation.org> In-Reply-To: References: <20260409120653.290386-1-devnexen@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: ECEED14000C X-Stat-Signature: 3oyj31tn97rie9oce4x3o6c8m3oj1bq4 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1775754893-96197 X-HE-Meta: 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 mf8L703+ W6gi3yOR50ofK0V49A4Okp6fN4mL5NM4gxL9MfzqfBe7PrZYB3QcIbbxMfLfyLsGgVYMY49DC8Fn1HpOyLvoXb0rjLTvXLadN3FrZrmMhLugfe8k2iOmdhHBjv0uoCqls7XRmhTw4NoY33nzEp7f2feKY+ST/0uy1VjBrzwrHyzMuCimoddYJN/pjjkx3SO2txMpQhAe04u0nC1icMwXOiEb80mpCts6yh4xN+senC+oDMCjIamdr9WrmEcNDmE5ivhWWaxopNfHzFJTky/YZ7MhxtQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 9 Apr 2026 19:04:49 +0200 "Vlastimil Babka (SUSE)" wrote: > On 4/9/26 14:06, David Carlier wrote: > > mfill_copy_folio_retry() drops mmap_lock for the copy_from_user() call. > > During this window, the VMA can be replaced with a different type (e.g. > > hugetlb), making the caller's ops pointer stale. Subsequent use of the > > stale ops can lead to incorrect folio handling or a kernel crash. > > > > Pass the caller's ops into mfill_copy_folio_retry() and compare against > > the current vma_uffd_ops() after re-acquiring the lock. Return -EAGAIN > > if they differ so the operation can be retried. > > > > Fixes: 59da5c32ffa3 ("userfaultfd: mfill_atomic(): remove retry logic") > > I don't have such sha1, is it a stale mm-unstable commit? Seems to be > 4974a6aaa768 ("userfaultfd: mfill_atomic(): remove retry logic") now in > mm-unstable (and can further change) Yup. I queued this as a squashable fix "userfaultfd-mfill_atomic-remove-retry-logic-fix.patch". Against Mike's "userfaultfd: mfill_atomic(): remove retry logic", queued for 2nd week of he merge window. I'll remove that Fixes: tag - it changes every day and results in "invalid Fixes:" emails from Mark.