Hi Suren On 2026/10/5 02:37, Suren Baghdasaryan wrote: > On Wed, Sep 30, 2026 at 5:25 AM Hao Ge <[email protected]> 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 <[email protected]> >>> wrote: >>>> >>>> On Tue, 29 Sep 2026 16:20:07 +0800 Hao Ge <[email protected]> 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/[email protected]/ > > I disagree with this approach. That means we are introducing an extra > code inside vm_module_tags_populate() only to clean it up later. > Instead please post Patch #2 separately. That posting should have your > current patch that changes vmap_pages_xxx() to clean up on failure, > followed by patch(es) which remove unnecessary cleanup that some > functions currently perform by themselves. This patchset should > definitely be tagged for stable.
You are right. Sorry for the confusion - my earlier deviation came from not fully understanding the rules for getting patches into the stable trees. > Once that patchset is accepted, the rest of your current patchset > fixing alloc_tags can be posted with correct assumption that > vmap_pages_range() cleans up its partial mapping when it fails. > > I know this sequence will take longer to upstream but I think it's the > right way to go. Make sense. Thanks for your continued support. Best Regards Hao > >> >> 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. >> >> >>> >>> The rest are also bug fixes but their size is concerning. I'll review >>> them first before advising on which ones should be backported. Some >>> fixes address issues that happen very rarely and if a fix is too >>> complex it might make sense to leave it be or fix it some other way >>> with less churn. Please give me a couple of days to review them. With >>> the upcoming LPC I'm trying to multiplex between several projects. >> >> Thanks, sorry for all the hassle on you folks. >> >> Thanks >> Best Regards >> Hao >> >>> >>> [1] >>> https://lore.kernel.org/all/[email protected]/ >>> >>>> >>>> Also, Sashiko has been busy again: >>>> >>>> https://sashiko.dev/#/patchset/[email protected]
