Hi Suren Thanks for your review.
On 2026/9/2 02:36, Suren Baghdasaryan wrote: > On Tue, Sep 1, 2026 at 8:04 AM Petr Pavlu <[email protected]> wrote: >> >> On 8/31/26 9:21 AM, Hao Ge wrote: >>> Whether a codetag section goes to the codetag region is decided by >>> layout_sections() and asked again in move_module(). A concurrent >>> load can shut profiling down in between, and move_module() then >>> copies the section to offset 0 of its regular destination, >>> overwriting whatever is there. >>> >>> Decide and allocate in one pass, before the layout. Allocation >>> errors fail the load. On a tag area overflow profiling is already >>> disabled, so -EAGAIN makes the section fall back to regular module >>> data and the module still loads. >>> >>> The overflow and populate failure paths of reserve_module_tags() now >>> release their reservation instead of leaking the maple tree entry. >>> When profiling was toggled off, the overflow check 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. >>> The check no longer depends on mem_alloc_profiling_enabled(). >>> >>> Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag >>> compression") >>> Reported-by: Sashiko <[email protected]> >>> Based-on-a-patch-by: Petr Pavlu <[email protected]> >>> Cc: Suren Baghdasaryan <[email protected]> >>> Signed-off-by: Hao Ge <[email protected]> >>> --- >>> Changes against Petr's prototype: >>> - allocate_codetag_sections() returns an error instead of void, and >>> only -EAGAIN falls back to a regular section. Any other error now >>> fails the load. The prototype fell back on everything, which can >>> leave live tags in module memory. >>> - reserve_module_tags() releases its reservation when populate fails >>> too, that path used to leak the maple tree entry. >>> - codetag_free_module_sections() on the move_module() error path uses >>> info->mod, the local mod is assigned only after a successful move. >>> - The percpu section is marked only when index.pcpu != 0, otherwise >>> sechdrs[0] gets marked. >>> - Dropped the SHF_ALLOC check, .codetag.* sections always have it. >>> --- >>> include/linux/module.h | 2 + >>> kernel/module/internal.h | 4 ++ >>> kernel/module/main.c | 120 ++++++++++++++++++++------------------- >>> mm/alloc_tag.c | 9 ++- >>> 4 files changed, 75 insertions(+), 60 deletions(-) >>> >>> diff --git a/include/linux/module.h b/include/linux/module.h >>> index 7566815fabbe..33548daa31a3 100644 >>> --- a/include/linux/module.h >>> +++ b/include/linux/module.h >>> @@ -325,6 +325,8 @@ enum mod_mem_type { >>> MOD_INIT_RODATA, >>> >>> MOD_MEM_NUM_TYPES, >>> + >>> + MOD_STANDALONE = -2, >>> MOD_INVALID = -1, >>> }; >>> >> >> It might be better to split this patch into two: the first to introduce >> MOD_STANDALONE and use it only for the percpu section, and the second >> with all the codetag-related changes. >> >> The introduction of SH_ENTSIZE_STANDALONE should also allow us to clean >> up the current resetting of SHF_ALLOC for the percpu section, and now >> also for codetag sections. The problem is that find_sec(".data..percpu") >> can currently return different results depending on whether it is called >> before layout_and_allocate() or later. In addition, apply_relocations() >> needs a special case for SH_ENTSIZE_STANDALONE, where it could otherwise >> just test SHF_ALLOC. >> >> Instead of resetting SHF_ALLOC for percpu/codetag sections, both >> __layout_sections() and move_module() can check for >> SH_ENTSIZE_STANDALONE to determine whether a section is handled >> specially and should be skipped. >> >> I think it would be useful to include this change in the first patch >> introducing MOD_STANDALONE, but I'm also ok with the current version. >> I can send a separate patch later to make more use of >> SH_ENTSIZE_STANDALONE in this way. > > I ran some tests on my side and nothing blew up. > Thanks. > Petr's suggestion to split the patch sounds good to me and > release_module_tags() change in alloc_tag.c could also be done in a > separate patch. It's the cleanup after we do shutdown_mem_profiling(), > so I think it would be correct on its own. OK, if I understand you correctly, you'd like the release_module_tags() call on vm_module_tags_populate() failure to go into its own separate patch. That's because our -EAGAIN fallback depends on the reserve_module_tags() change. Without it the overflow entry stays in the maple tree, codetag_module_replaced() retargets it at the live module, and rmmod then walks the never-populated tag area and faults. Thanks Best Regards Hao > Thanks, > Suren. > >> >>> @@ -2966,18 +2967,23 @@ static struct module *layout_and_allocate(struct >>> load_info *info, int flags) >>> */ >>> module_mark_ro_after_init(info->hdr, info->sechdrs, info->secstrings); >>> >>> - /* >>> - * Determine total sizes, and put offsets in sh_entsize. For now >>> - * this is done generically; there doesn't appear to be any >>> - * special cases for the architectures. >>> - */ >>> + /* Allow codetag sections to be allocated separately first. */ >>> + err = allocate_codetag_sections(info); >>> + if (err) { >>> + codetag_free_module_sections(info->mod); >> >> The usual convention is that functions clean up after themselves on >> error. That means this codetag_free_module_sections() call should be >> done ideally by allocate_codetag_sections(). >> >> -- >> Thanks, >> Petr
