On Tue, Aug 11, 2026 at 10:41 PM Hao Ge <[email protected]> wrote: > > In reserve_module_tags(), the tag overflow check is gated on > mem_alloc_profiling_enabled(): > > if (mem_alloc_profiling_enabled() && !tags_addressable()) > > If profiling is toggled off at runtime and a module is loaded whose > tags exceed the compressed-mode limit, shutdown_mem_profiling() is > skipped. vm_module_tags_populate() still maps memory for the tags and > the module loads successfully, but the total tag count now exceeds what > NR_UNUSED_PAGEFLAG_BITS can address. > > Once profiling is re-enabled, ref_to_idx() computes each tag's index > as its position in the alloc_tag array. update_page_tag_ref() masks > it to alloc_tag_ref_mask before storing in page->flags. Indices > beyond the mask are truncated and idx_to_ref() resolves them to wrong > tags. > > This silently corrupts /proc/allocinfo: allocated pages get attributed > to the wrong call sites, so the statistics it reports are wrong. > > mem_alloc_profiling_enabled() and mem_profiling_compressed are > independent. Once compressed mode is established at boot, it stays > active regardless of runtime toggles of mem_profiling. > > Remove the mem_alloc_profiling_enabled() guard. On overflow, shut down > profiling, release the reservation, and return -EAGAIN so that > layout_and_allocate() retries with profiling disabled: codetag sections > are then placed as regular module data and the module loads without > profiling rather than being rejected entirely. > > Fixes: 4835f747d3ed ("alloc_tag: support for page allocation tag compression") > Cc: [email protected] > Suggested-by: Suren Baghdasaryan <[email protected]> > Signed-off-by: Hao Ge <[email protected]>
I'm looking at your fixes for pre-existing issues reported by Sashiko but this patch looks correct to me. Acked-by: Suren Baghdasaryan <[email protected]> > --- > kernel/module/main.c | 25 +++++++++++++++++++++++-- > mm/alloc_tag.c | 8 +++++--- > 2 files changed, 28 insertions(+), 5 deletions(-) > > diff --git a/kernel/module/main.c b/kernel/module/main.c > index 46dd8d25a605..ed26f167be84 100644 > --- a/kernel/module/main.c > +++ b/kernel/module/main.c > @@ -2944,6 +2944,7 @@ static struct module *layout_and_allocate(struct > load_info *info, int flags) > { > struct module *mod; > int err; > + unsigned long frob_size[MOD_MEM_NUM_TYPES]; > > /* Allow arches to frob section contents and sizes. */ > err = module_frob_arch_sections(info->hdr, info->sechdrs, > @@ -2966,18 +2967,38 @@ static struct module *layout_and_allocate(struct > load_info *info, int flags) > */ > module_mark_ro_after_init(info->hdr, info->sechdrs, info->secstrings); > > + /* > + * Save the sizes reserved by module_frob_arch_sections() so they can > + * be restored if we retry below. > + */ > + for_each_mod_mem_type(type) > + frob_size[type] = info->mod->mem[type].size; > + > /* > * 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. > */ > +retry: > layout_sections(info->mod, info); > layout_symtab(info->mod, info); > > /* Allocate and move to the final place */ > err = move_module(info->mod, info); > - if (err) > - return ERR_PTR(err); > + if (err) { > + if (err != -EAGAIN) > + return ERR_PTR(err); > + /* > + * -EAGAIN means profiling was disabled but the module > + * can still load without it. Reset state and retry. > + */ > + rewrite_section_headers(info, flags); > + for_each_mod_mem_type(type) > + info->mod->mem[type].size = frob_size[type]; > + info->sechdrs[info->index.sym].sh_flags &= ~(unsigned > long)SHF_ALLOC; > + info->sechdrs[info->index.str].sh_flags &= ~(unsigned > long)SHF_ALLOC; > + goto retry; > + } > > /* Module has been copied to its final place now: return it. */ > mod = (void *)info->sechdrs[info->index.mod].sh_addr; > diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c > index af44f90379f2..0a7b657fe2de 100644 > --- a/mm/alloc_tag.c > +++ b/mm/alloc_tag.c > @@ -950,10 +950,12 @@ static void *reserve_module_tags(struct module *mod, > unsigned long size, > int grow_res; > > module_tags.size = offset + size; > - if (mem_alloc_profiling_enabled() && !tags_addressable()) { > + if (!tags_addressable()) { > shutdown_mem_profiling(true); > - pr_warn("With module %s there are too many tags to > fit in %d page flag bits. Memory allocation profiling is disabled!\n", > - mod->name, NR_UNUSED_PAGEFLAG_BITS); > + pr_warn_once("With module %s there are too many tags > to fit in %d page flag bits. Memory allocation profiling is disabled!\n", > + mod->name, NR_UNUSED_PAGEFLAG_BITS); > + release_module_tags(mod, false); > + return ERR_PTR(-EAGAIN); > } > > grow_res = vm_module_tags_populate(); > -- > 2.25.1 >
