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b=WmGqQ8vjDV4ZvaVH0iE/01aNlECAJH5GwTvX/6N/C9UCOON+ZhEYc3GRFoVdtqlVP Pe+U4KcjjA2eNCttCtcX40ltu8dhR7FldWOGqSFoLE1Y5FpKD43ejXBYFmSltjxCVA Qhd2mi7zwjvAAky8ZGiu9TKD+Qp1A66NHbqKgQRY= Date: Fri, 8 May 2026 14:51:21 -0700 From: Andrew Morton To: Wei Yang Cc: david@kernel.org, ljs@kernel.org, riel@surriel.com, liam@infradead.org, vbabka@kernel.org, harry@kernel.org, jannh@google.com, sj@kernel.org, ziy@nvidia.com, balbirs@nvidia.com, linux-mm@kvack.org, Lorenzo Stoakes , stable@vger.kernel.org Subject: Re: [PATCH] mm/page_vma_mapped: revalidate and do proper check before return device-private pmd Message-Id: <20260508145121.35e2552d403b94ea6f748b90@linux-foundation.org> In-Reply-To: <20260508013728.21285-1-richard.weiyang@gmail.com> References: <20260508013728.21285-1-richard.weiyang@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-Server: rspam03 X-Rspamd-Queue-Id: 7CF174000F X-Stat-Signature: hnumfc9adyep6we9u8xrouniedh8jeug X-Rspam-User: X-HE-Tag: 1778277083-647189 X-HE-Meta: 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 v2c0mP28 XEIRK3UC9XmeMcYNq5oSeo6Z75Kemv0l6LNys6v9Ry4u4fFcHDO7mspzCLkhKCSLPaIXcbsBk8B5nChnLbW/bNpRxZX4AV9LGgtKdOnhWzZqRhIoDoRUCG/gy0ynEdmvRCHaNJdIhi1xfGkmFFeQXyIbNsEv1DesZsPRDd/h6ci5rva7aQ/dVxE5dXdsFHhwPe8jERc1/1Ggi6nqzVsZ1j8emWPVrb4ewiJztknlI7GPJVkFv7kZ2z3AQoUzrVIOEX45EQeMGExe++2CMtjWlUaKOkdt/oNofcI8YBtPAmW78NHjtvav+Hgc5aX6UEZ22COmDVQeLefKviZAgkXSN6CdIhgTo4UzmUCwgRbXNA9QCqsT13nTYRaqyxFjb2c7wxncHsO1mRVgoi2hjC80Qhs99Xc1DBavxyT16L08N5M9oM5HGy8BzQp8VWgTPtQYecVemXizdzGjeMU50dCFFXz+XfA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 8 May 2026 01:37:28 +0000 Wei Yang wrote: > For pmd_trans_huge() and pmd_is_migration_entry(), we does following > before return the pmd entry: > > * re-validate pmd entry > * check PVMW_MIGRATION > * check_pmd() > * handle on pte level if split under us > > But for device-private pmd, we just return after pmd_lock(). This may > lead to inproper situation. What is "improper situation"? > This patch fixes commit 65edfda6f3f2 ("mm/rmap: extend rmap and migration > support device-private entries") by following the same pattern as > pmd_trans_huge() and pmd_is_migration_entry(). > > Fixes: 65edfda6f3f2 ("mm/rmap: extend rmap and migration support device-private entries") > Signed-off-by: Wei Yang > Cc: David Hildenbrand > Cc: Balbir Singh > Cc: SeongJae Park > Cc: Zi Yan > Cc: Lorenzo Stoakes > Cc: If we're to propose a fix for -stable backporting I believe we should fully explain to -stable maintainers *why* we're making that proposal. IOW, and not for the first time(!), what are the worst-case userspace-visible effects of this bug?