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Howlett" , Vlastimil Babka , Shakeel Butt , David Hildenbrand , Mike Rapoport , Michal Hocko , Uladzislau Rezki , Toshi Kani , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Kiryl Shutsemau , Catalin Marinas , Will Deacon , Dev Jain , Ryan Roberts , David Carlier , linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "Denis V. Lunev" , "Borah, Chaitanya Kumar" , stable@vger.kernel.org, syzbot+fd95a72470f5a44e464c@syzkaller.appspotmail.com Subject: Re: [PATCH mm-hotfixes v6 0/5] mm: fix UAF caused by race between ptdump and vmap pgtable freeing Message-Id: <20260723162646.350cf3bf415a0855140d139b@linux-foundation.org> In-Reply-To: <20260723-series-vmap-race-fix-v6-0-8cc77dcc0018@kernel.org> References: <20260723-series-vmap-race-fix-v6-0-8cc77dcc0018@kernel.org> 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: CDDF640003 X-Stat-Signature: dzrm5ibakotw4yf5fy1pfrj3p4c77gu3 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1784849208-55165 X-HE-Meta: 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 x+yviuXw Ig9yPDAzk9DveUjHJSCHdXmDotnAZxSElNwcwxQShFgSeSLG2aOWNpE0Ha+QgU+f75yd4d9P20GvwE7lkwR7kop5plx/4DRf+iUcbS6AsRa5fSlbS6KiSGqVuAWYMq72cJ20WvAoztkaDicuy6XY9M3KgiIf9AeFoc5hz7CXwVVVD1N7x7vVle+xkxQRoJaO1E5g2GRXaCnj3faSDOOmyVfotlQfv4WYcdGqhFsqYo4h2rZjOunbE8txF3xHJsjclembJoARvC8Wdo1rHfmzUIbqzx0RQaQKUngEWmUWWSgPugKU7yEv8lD/T+BWnDE628kycuocte0wmmXpxiKqUIyVYcLwVzanmsiwnJZfL3i+19gLKzWsbquhaX0W8KZ8inJhxV3AFGQMur/GXlcsLIrS03A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 23 Jul 2026 16:16:30 +0100 "Lorenzo Stoakes (ARM)" wrote: > Kernel page table walkers fall into two broad categories - those ranges > where no exclusion is required via walk_kernel_page_table_range_lockless() > and those where exclusion is required via walk_kernel_page_table_range() > or walk_page_range_debug(). > > ... > > This series works around this by #ifndef CONFIG_ARM64'ing the mmap read > lock in vmap logic, then partially reverting commit fa93b45fd397 ("arm64: > Enable vmalloc-huge with ptdump"), keeping the enablement of huge vmap > support, and removing the ifdeffery with the partial revert patch. > > ... > Thanks, I updated the mm-hotfixes-unstable branch to this version. > --- > v6: > * Rebased on latest master of Linus's tree. > * Updated: 3/5 to drop the init_mm lock over page table allocation in order > to avoid deadlocks due to init_mm -> ... -> fs_reclaim -> init_mm > dependency cycles, as reported by Chaitanya with thanks! > * Small cover letter typo fixes. Here's how v6 altered mm.git: arch/x86/mm/pat/set_memory.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/arch/x86/mm/pat/set_memory.c~b +++ a/arch/x86/mm/pat/set_memory.c @@ -50,7 +50,8 @@ struct cpa_data { unsigned int flags; unsigned int force_split : 1, force_static_prot : 1, - force_flush_all : 1; + force_flush_all : 1, + init_mm_read_locked : 1; struct page **pages; }; @@ -1250,7 +1251,11 @@ static int split_large_page(struct cpa_d if (!debug_pagealloc_enabled()) spin_unlock(&cpa_lock); + if (cpa->init_mm_read_locked) + mmap_read_unlock(&init_mm); ptdesc = pagetable_alloc(GFP_KERNEL, 0); + if (cpa->init_mm_read_locked) + mmap_read_lock(&init_mm); if (!debug_pagealloc_enabled()) spin_lock(&cpa_lock); if (!ptdesc) @@ -2123,8 +2128,10 @@ static int change_page_attr_set_clr(unsi cpa.force_split = force_split; /* Avoid race with concurrent CPA collapse. */ + cpa.init_mm_read_locked = true; scoped_guard(mmap_read_lock, &init_mm) ret = __change_page_attr_set_clr(&cpa, 1); + cpa.init_mm_read_locked = false; /* * Check whether we really changed something: _