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Fri, 09 Oct 2026 08:22:52 +0000 X-Mizu-Trace-ID: 23e08e172bfdef72 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Fri, 9 Oct 2026 16:23:53 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 2/7] mm/vmalloc: undo partial mappings inside the mapping functions To: Suren Baghdasaryan , Uladzislau Rezki Cc: Kent Overstreet , Luis Chamberlain , Petr Pavlu , Daniel Gomez , Sami Tolvanen , Aaron Tomlin , Andrew Morton , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Vlastimil Babka , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, Sashiko , stable@vger.kernel.org References: <20260929082014.160587-1-hao.ge@linux.dev> <20260929082014.160587-3-hao.ge@linux.dev> Content-Language: en-US From: Hao Ge In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 27D1318000A X-Rspam-User: X-Stat-Signature: xjt3r345gp9g6azjots8esduqzxyarpy X-HE-Tag: 1791534174-66189 X-HE-Meta: U2FsdGVkX1/BMZvqrJ+D/Ep+Ni18nulcgUmQieFjWbVorAFzaMMxbAfpiAVN6eaQdgT4vKIyXPbWJwev3kvbmZO89cwWW1O4mxOyKd4QrBchLGJNnoPJzdk84Rno/JDvVhh/rtsERAh8JwrTEITJvkZyspDsin1eg4yCOEwC8buukispwrF2JsJMDIZ0NbOznVC+KuDZLhRzNyETk6Hey7E/9tUhhPuibIm7UGgg4dCEFYNcFlKLTiUJ34Jp1CFgIGgf4o8sEB8Zdu6ifyKESanGMYxRa6nedwXCdlS717K/e+1uQ3qjU2nFEYGKr8PQg2jXzfay9bRPMo9K7CxMg+ub9A1931Oc92K0tf5mtlw6GoY1fAjwGr/Lcr6HCu5lyE4Bq26QI3xfrrVRe92XGYp/pGo0JCbsVUKeTyA3Sbqb7241JEgUaQcJOa/J1bVD/kj8aCPkeZKAS1epgrmtOz8pRAYVV8vCEJ9YhnUjQcigraWGjFAregXFbXaphi5pd+2sYFpJpZHXOAPTgsG6T6JW8xQqaRXZZxlaGZs2+6vN79ryS40zl9D84DOgXstTDJ+bhEIRcotP3nXFuLtYQsD35dRLzW/gS/5+9T2EAEG/UKTollSwWUM4l4dlceK1UzwjXaceCRtkzqTy3QGdyN+LAfzjcFeD+t3M1LZmBSCfrv1/GjBwBDU+S+OwpoH9GeCHe9vUvV6Eesagn1Ah3OJ5UZMHm/l+8Oeor0/cfdNfO7h5TJRrlDSnY3xZTiJLX1piDEfQi22eICeJpB4gQVNIbvBYrZKUSdomfYEBN04FX97y3pU9IIRYJSbJSUq3VEPlYUHw4xsoMLLDwS6h/OzPFty6PYdcbcpPTEHPzHN07XpKS69raE1i1OV+KpYhENLbS67sQsxEHpVim6lLMTsKw1NonBCmLdfuzOd0aucL4NAmVDXf0nzzOkzroD04I5nW21wFgiyWzXPy6xv Tnbh2Z13 CIThibhwmeMg9Ujr4ND+SL8a+Uc/66ebebanLJpg8nM1oSfzb5vs8vhXsAl72zea+E4Ub4/Ytq2AFYYN4+t+BW1tjXsgPvaoNHt3o5P1tZ805itTaXyI7MSCw4eHZ4aYEDxDMk97achvxhZe0SexxM4KWbip93jClUJ7gImgkqndVz3LRgxaZ6IsmOrlsgP5tylF2p7e3OQ8LXtr0x+jesXaOS/YN/2Os41CgAeZnl3XVF6rCGKDIfbFs0nCXJ7B3CcwDH+hXTXZL0GbasULIpcRxCurAB9H771tCk1ixRQtiGJEiwY5Vm127+RTUXwby7erK7LbHzww+T30n8fMQbAd74DoK4UPhjYEv Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Suren On 2026/10/5 01:42, Suren Baghdasaryan wrote: > On Wed, Sep 30, 2026 at 12:12 PM Uladzislau Rezki wrote: >> >> On Tue, Sep 29, 2026 at 04:20:09PM +0800, Hao Ge 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. For example, pcpu_map_pages() and >>> kmsan_ioremap_page_range() unmap the leftovers themselves, while >>> vm_module_tags_populate() and the __GFP_NOFAIL retry loop in >>> __vmalloc_area_node() relied on the mapping functions cleaning up and >>> did not call anything like vunmap_range() themselves. When the same >>> range is mapped again, the attempt hits the leftovers and fails, with >>> BUG() in vmap_pte_range() for huge mappings. >>> >>> After discussing with Suren and Ulad, we decided the cleanup belongs >>> to __vmap_pages_range_noflush() and friends, so the callers no longer >>> need to unmap the partial mappings themselves. Each function now >>> undoes the PTEs it installed itself. >>> >>> The rollback calls the low-level __vunmap_range_noflush(), it just >>> clears the PTEs of the range it is given, which is all a rollback >>> needs. It cannot use vunmap_range_noflush() because these mapping >>> functions also map the KMSAN shadow and origin, and for a metadata >>> range its hook would look up the metadata of the metadata, get 0 >>> and BUG() on addr >= end. The failed mappings were never accessed, >>> no TLB flush needed. >>> >>> Fixes: 9376130c390a ("mm/vmalloc: add support for __GFP_NOFAIL") >>> Fixes: 0f9b685626da ("alloc_tag: populate memory for module tags as needed") > > I don't think this fixes 0f9b685626da. I mean it fixes it but > indirectly. That patch expects vmap_pages_range() to undo the mappings > when it fails, which is a reasonable assumption. By fixing > vmap_pages_xxx we fix all its users, including > vm_module_tags_populate(). So, it indirectly fixes several callers but > when adding a Fixes tag we do not list all patches we indirectly fix. > Got it, learned something new here. I used to think we had to add a Fixes tag so stable folks know which branches to backport to. I went back and re-read Documentation/process/stable-kernel-rules.rst, and turns out that's not how it works. Both Fixes tags should be removed then. At the end of the day we're just normalizing the API; those other commits are merely beneficiaries of this change. Thanks for your patient guidance. Best Regards Hao >>> Reported-by: Sashiko >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Hao Ge >>> --- >>> mm/kmsan/shadow.c | 4 ++++ >>> mm/vmalloc.c | 31 +++++++++++++++++++++++++++++-- >>> 2 files changed, 33 insertions(+), 2 deletions(-) >>> >>> diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c >>> index 0c88d89bf0d6..2166086d3dc3 100644 >>> --- a/mm/kmsan/shadow.c >>> +++ b/mm/kmsan/shadow.c >>> @@ -258,6 +258,10 @@ int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end, >>> o_pages, page_shift); >>> kmsan_leave_runtime(); >>> if (mapped) { >>> + /* Undo the shadow mapping set up above. */ >>> + kmsan_enter_runtime(); >>> + __vunmap_range_noflush(shadow_start, shadow_end); >>> + kmsan_leave_runtime(); >>> err = mapped; >>> goto ret; >>> } >>> >> Can we just do that inside the vmalloc? For example in the >> __vmap_pages_range_noflush() as entry function for all(?) helpers? >> So we do not need do it manually? > > Agree, that would be better. > >> >>> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >>> index 859e6d2d57a3..9bbf75706627 100644 >>> --- a/mm/vmalloc.c >>> +++ b/mm/vmalloc.c >>> @@ -349,6 +349,10 @@ static int vmap_range_noflush(unsigned long addr, unsigned long end, >>> if (mask & ARCH_PAGE_TABLE_SYNC_MASK) >>> arch_sync_kernel_mappings(start, end); >>> >>> + /* Undo the PTEs installed before the failure. */ >>> + if (err) >>> + __vunmap_range_noflush(start, end); >>> + >>> return err; >>> } >>> >>> @@ -363,6 +367,9 @@ 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; >>> } >>> >>> @@ -667,6 +674,10 @@ static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end, >>> if (mask & ARCH_PAGE_TABLE_SYNC_MASK) >>> arch_sync_kernel_mappings(start, end); >>> >>> + /* Undo the PTEs installed before the failure. */ >>> + if (err) >>> + __vunmap_range_noflush(start, end); >>> + >>> return err; >>> } >>> >> The only one user of that function is __vmap_pages_range_noflush() >> so we can cover both cases there small and huge path. >> >> Is that enough just to do unroll in the below: >> >> __vmap_pages_range_noflush() >> vmap_page_range() >> >> functions? It will also fix NOFAIL case: >> >> >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index 89c327a6ce7d..fa1f357ecf3f 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -359,10 +359,19 @@ int vmap_page_range(unsigned long addr, unsigned long end, >> >> err = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot), >> ioremap_max_page_shift); >> + if (err) >> + goto error_cleanup_range; >> + >> flush_cache_vmap(addr, end); >> - if (!err) >> - err = kmsan_ioremap_page_range(addr, end, phys_addr, prot, >> + err = kmsan_ioremap_page_range(addr, end, phys_addr, prot, >> ioremap_max_page_shift); >> + if (err) >> + goto error_cleanup_range; >> + >> + return 0; >> + >> +error_cleanup_range: >> + __vunmap_range_noflush(addr, end); >> return err; >> } >> >> @@ -683,26 +692,35 @@ 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; >> >> - WARN_ON(page_shift < PAGE_SHIFT); >> - >> - if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || >> - page_shift == PAGE_SHIFT) >> - return vmap_small_pages_range_noflush(addr, end, prot, pages); >> + if (WARN_ON(addr >= end)) >> + return -EINVAL; >> >> - for (i = 0; i < nr; i += 1U << (page_shift - PAGE_SHIFT)) { >> - int err; >> + if (WARN_ON(page_shift < PAGE_SHIFT)) >> + return -EINVAL; >> >> - err = vmap_range_noflush(addr, addr + (1UL << page_shift), >> + if (!IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || >> + 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; >> + if (err) >> + __vunmap_range_noflush(start, end); >> + >> + /* 0 on success. */ >> + return err; >> } >> >> int vmap_pages_range_noflush(unsigned long addr, unsigned long end, >> @@ -714,7 +732,13 @@ 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); >> + if (ret) >> + /* Cleanup KMSAN metadata. */ >> + kmsan_vunmap_range_noflush(addr, end); >> + >> + return ret; >> } >> >> static int __vmap_pages_range(unsigned long addr, unsigned long end, >> >> >> -- >> Uladzislau Rezki