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Wed, 30 Sep 2026 01:34:06 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 30 Sep 2026 10:34:03 +0200 To: Hao Ge Cc: Suren Baghdasaryan , Andrew Morton , Kent Overstreet , Luis Chamberlain , Petr Pavlu , Daniel Gomez , Sami Tolvanen , Aaron Tomlin , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Vlastimil Babka , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com Subject: Re: [PATCH v11 0/7] alloc_tag and module codetag section fixes Message-ID: References: <20260929082014.160587-1-hao.ge@linux.dev> <20260929134401.a1a385ff4369661f879b5d2f@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Wed, Sep 30, 2026 at 11:26:41AM +0800, Hao Ge wrote: > Hi Suren and Andrew > > > On 2026/9/30 10:39, Suren Baghdasaryan wrote: > > On Tue, Sep 29, 2026 at 8:44 PM Andrew Morton wrote: > >> > >> On Tue, 29 Sep 2026 16:20:07 +0800 Hao Ge wrote: > >> > >>> With profiling toggled off, the overflow check in > >>> reserve_module_tags() did not run, a module could load with more > >>> tags than the page flags can address, and re-enabling profiling > >>> then silently corrupted /proc/allocinfo. On overflow the fix shuts > >>> profiling down, releases the reservation and returns -EAGAIN, and > >>> the codetag section lands as regular module data in the same load, > >>> so the module loads without profiling. > >>> > >>> Review of the earlier series by Sashiko turned up more problems. > >>> > >>> One is a race. layout_sections() and move_module() both asked > >>> codetag_needs_module_section() where a codetag section goes, and > >>> mem_profiling_support can change between the two calls, for instance > >>> when another module load overflows the tag index and shuts profiling > >>> down. move_module() then copied the codetag section to offset 0 of > >>> its regular destination and clobbered the first section placed in > >>> that region. > >>> > >>> v7 reworks where codetag sections are allocated, on a prototype by > >>> Petr Pavlu [1]. The allocation runs before layout_sections() and the > >>> placement is decided in one step, so nothing re-asks the question > >>> and the race is gone. The retry is gone too, on -EAGAIN the section > >>> is laid out as regular module data right in the same load. > >> > >> Thanks. > >> > >> Seven patches, all cc:stable. Why is a backport proposed? > >> Documentation/process/stable-kernel-rules.rst gives guidelines - does > >> this series meet them? Does Suren have thoughts? > > Thanks, I've just gone through this carefully. > > > > > I think vmalloc fix in patch#2 should be posted separately and clearly > > quialifies for backporting as if fixes issues Hao found at [1]. > > Agreed. Patch #2 was added to this patch series because vm_module_tags_populate > suffers from the same issue. If we want to be more conservative, I'd prefer to keep > vm_module_tags_populate as it was in V10: > https://lore.kernel.org/all/20260915070001.113559-3-hao.ge@linux.dev/ > > Then we can submit a fix for __GFP_NOFAIL retry loop in __vmalloc_area_node() as a hotfix together > with our new patch #2. While at it, we can also check if there are any unnecessary calls to > vunmap_range family functions that can be cleaned up now that patch #2 is applied. > Yep, this should be a separate fix for vmalloc. -- Uladzislau Rezki