[RFC PATCH 2/4] mm/vmalloc: undo partial mappings inside the mapping functions
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HOTtoday
From: Hao Ge <hao.ge@linux.dev>
Date: 2026-10-09 06:36:10
Also in:
linux-mm, lkml
Subsystem:
memory management, the rest, vmalloc · Maintainers:
Andrew Morton, Linus Torvalds, Uladzislau Rezki
__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 <sashiko-bot@kernel.org> Suggested-by: Uladyslau Rezki <urezki@gmail.com> Signed-off-by: Hao Ge <hao.ge@linux.dev> --- 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); + + 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,
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2.25.1