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Fri, 09 Oct 2026 06:36:05 +0000 X-Mizu-Trace-ID: bf8d544524139af5 X-Migadu-Flow: FLOW_OUT From: Hao Ge To: Suren Baghdasaryan , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter , Uladzislau Rezki Cc: Hao Ge , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Sashiko Subject: [RFC PATCH 2/4] mm/vmalloc: undo partial mappings inside the mapping functions Date: Fri, 9 Oct 2026 14:36:17 +0800 Message-Id: <20261009063619.112313-3-hao.ge@linux.dev> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20261009063619.112313-1-hao.ge@linux.dev> References: <20261009063619.112313-1-hao.ge@linux.dev> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 05D4140005 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: q5rf1dtnywtagt9w9o6pbc11u145kmub X-HE-Tag: 1791527766-970803 X-HE-Meta: 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 WkkAKDZK dGmEsk4VRoe1KgEIgXt9hFhFDg6wjaaQZsXa1WSKmXoCQjaGezjwPLGI+VGYUuWXo7O7X4xzIB7tXPzLoP+wp+30NR9YgRnQUo7WhN1lquDGL0WQ6Vd2qmf8iH++nnHyj3ndNbcxGNhEV3sXLViqnKnMXBUGi3EgV+bDtw8r+2a0L/5nsijDCGS/X28Khz1izV+3MfZJmFY/js99gCdX9PLveSRyWSN6NHv+Z4Q16S1uwDu0h1WinFCUMsDr1p5xeL4Hkz5iBSggY0GeH+v7t6+QpeWaToaVflRumhBoiz3Z5ZRweo2oqrCzg6eaHvRA/i7DcUZHVTLa1bisBoGdb9hXKXE4YClxymQRI Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: __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 Suggested-by: Uladyslau Rezki Signed-off-by: Hao Ge --- 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, -- 2.25.1