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Wed, 23 Sep 2026 09:33:18 -0700 (PDT) From: Mikhail Gavrilov To: Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org Cc: "H . Peter Anvin" , Mike Rapoport , Lorenzo Stoakes , Toshi Kani , linux-mm@kvack.org, regressions@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/mm: avoid a reclaiming allocation in pud_free_pmd_page() Date: Wed, 23 Sep 2026 21:33:15 +0500 Message-ID: <20260923163315.275046-1-mikhail.v.gavrilov@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260916062222.27347-1-mikhail.v.gavrilov@gmail.com> References: <20260916062222.27347-1-mikhail.v.gavrilov@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 050D6100009 X-Stat-Signature: k494r6eor94ia9whhy8gmboyxsuowdtn X-Rspam-User: X-HE-Tag: 1790181200-503749 X-HE-Meta: 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 CDNp7bxw 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, The lock cycle this patch breaks has meanwhile reached released stable kernels: d5d8b8662e6e ("x86/mm/pat: Acquire init_mm read lock on attribute changes to avoid UAF") went out in 7.2.7 and 6.18.53 on Sep 21. Both trees already carry 26444eb71465 ("mm/vmalloc: acquire init_mm lock on huge vmap to avoid ptdump UAF"), and pud_free_pmd_page() there still allocates with GFP_KERNEL under the init_mm lock, so the cycle quoted in the patch exists there too, not only in 7.3-rc. The patch still applies cleanly to current mainline and next-20260922, and the reproducer below the scissors of the original mail works unchanged. Dave, could this go in through x86/urgent for 7.3? Lorenzo, since the rule it applies comes from your series, a review from you would help. If either of you would rather fix it differently, I am happy to respin. -- Thanks, Mikhail