On Fri, Oct 9, 2026 at 10:36 AM Hao Ge <[email protected]> wrote: > > __vmap_pages_range_noflush() and friends can install some PTEs before > failing and leave them mapped, and the kernel callers do not agree on > who cleans them up. pcpu_map_pages() and kmsan_ioremap_page_range() > roll back what they mapped before the failure, while > vm_module_tags_populate() and the __GFP_NOFAIL retry loop in > __vmalloc_area_node() rely on the mapping functions cleaning up and > do not call anything like vunmap_range() themselves. When the same > range is mapped again, the attempt hits the leftovers and fails, with > a BUG() in vmap_pte_range() for huge mappings and a warning on the > small-page path. > > After discussing with Suren and Ulad, we decided to put the rollback > into the entry points of the vmap API rather than into every low-level > helper. __vmap_pages_range_noflush() undoes the whole range it was > asked to map when it fails, and vmap_page_range() undoes its range > for the ioremap-style mappings. > > The rollback is __vunmap_range_noflush(), it only clears the PTEs, > no TLB flush, nothing has touched these mappings. > vmap_pages_range_noflush() drops the KMSAN metadata when the data > mapping fails, and an empty range bails out with -EINVAL now, which > used to BUG_ON() on the small-page path and map nothing at all on > the huge-page one. > > Reported-by: Sashiko <[email protected]> > Suggested-by: Uladyslau Rezki <[email protected]> > Signed-off-by: Hao Ge <[email protected]> > --- > mm/vmalloc.c | 44 ++++++++++++++++++++++++++++++++------------ > 1 file changed, 32 insertions(+), 12 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index db669103dc66..e1b376f57dd2 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -363,6 +363,9 @@ int vmap_page_range(unsigned long addr, unsigned long end, > if (!err) > err = kmsan_ioremap_page_range(addr, end, phys_addr, prot, > ioremap_max_page_shift); > + if (err) > + __vunmap_range_noflush(addr, end); > + > return err; > } > > @@ -683,27 +686,35 @@ int __vmap_pages_range_noflush(unsigned long addr, > unsigned long end, > pgprot_t prot, struct page **pages, unsigned int page_shift) > { > unsigned int i, nr = (end - addr) >> PAGE_SHIFT; > + unsigned long start = addr; > + int err = 0; > + > + if (WARN_ON_ONCE(addr >= end)) > + return -EINVAL; > > if (WARN_ON_ONCE(page_shift < PAGE_SHIFT)) > return -EINVAL; > > if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || > - page_shift == PAGE_SHIFT) > - return vmap_small_pages_range_noflush(addr, end, prot, pages); > - > - for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) { > - int err; > - > - err = vmap_range_noflush(addr, addr + (1UL << page_shift), > + page_shift == PAGE_SHIFT) { > + err = vmap_small_pages_range_noflush(addr, end, prot, pages); > + } else { > + for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) { > + err = vmap_range_noflush(addr, addr + (1UL << > page_shift), > page_to_phys(pages[i]), prot, > page_shift); > - if (err) > - return err; > + if (err) > + break; > > - addr += 1UL << page_shift; > + addr += 1UL << page_shift; > + } > } > > - return 0; > + /* Undo the PTEs installed before the failure. */ > + if (err) > + __vunmap_range_noflush(start, end);
Would it be too complicated to track how much was actually mapped and unmap only that portion? > + > + return err; > } > > int vmap_pages_range_noflush(unsigned long addr, unsigned long end, > @@ -715,7 +726,16 @@ int vmap_pages_range_noflush(unsigned long addr, > unsigned long end, > > if (ret) > return ret; > - return __vmap_pages_range_noflush(addr, end, prot, pages, page_shift); > + > + ret = __vmap_pages_range_noflush(addr, end, prot, pages, page_shift); > + /* > + * The page tables undo themselves on failure. Tear down the > + * metadata that was fully set up before the mapping failed. > + */ > + if (ret) > + kmsan_vunmap_range_noflush(addr, end); > + > + return ret; > } > > static int __vmap_pages_range(unsigned long addr, unsigned long end, > -- > 2.25.1 >
