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]/ 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]
