kernel/linux.git/mm/memory.c, branch v6.12.80

mm/memory: do not populate page table entries beyond i_size

2025-11-24T09:36:07+00:00

commit 74207de2ba10c2973334906822dc94d2e859ffc5 upstream. Patch series "Fix SIGBUS semantics with large folios", v3. Accessing memory within a VMA, but beyond i_size rounded up to the next page size, is supposed to generate SIGBUS. Darrick reported[1] an xfstests regression in v6.18-rc1. generic/749 failed due to missing SIGBUS. This was caused by my recent changes that try to fault in the whole folio where possible: 19773df031bc ("mm/fault: try to map the entire file folio in finish_fault()") 357b92761d94 ("mm/filemap: map entire large folio faultaround") These changes did not consider i_size when setting up PTEs, leading to xfstest breakage. However, the problem has been present in the kernel for a long time - since huge tmpfs was introduced in 2016. The kernel happily maps PMD-sized folios as PMD without checking i_size. And huge=always tmpfs allocates PMD-size folios on any writes. I considered this corner case when I implemented a large tmpfs, and my conclusion was that no one in their right mind should rely on receiving a SIGBUS signal when accessing beyond i_size. I cannot imagine how it could be useful for the workload. But apparently filesystem folks care a lot about preserving strict SIGBUS semantics. Generic/749 was introduced last year with reference to POSIX, but no real workloads were mentioned. It also acknowledged the tmpfs deviation from the test case. POSIX indeed says[3]: References within the address range starting at pa and continuing for len bytes to whole pages following the end of an object shall result in delivery of a SIGBUS signal. The patchset fixes the regression introduced by recent changes as well as more subtle SIGBUS breakage due to split failure on truncation. This patch (of 2): Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are supposed to generate SIGBUS. Recent changes attempted to fault in full folio where possible. They did not respect i_size, which led to populating PTEs beyond i_size and breaking SIGBUS semantics. Darrick reported generic/749 breakage because of this. However, the problem existed before the recent changes. With huge=always tmpfs, any write to a file leads to PMD-size allocation. Following the fault-in of the folio will install PMD mapping regardless of i_size. Fix filemap_map_pages() and finish_fault() to not install: - PTEs beyond i_size; - PMD mappings across i_size; Make an exception for shmem/tmpfs that for long time intentionally mapped with PMDs across i_size. Link: https://lkml.kernel.org/r/20251027115636.82382-1-kirill@shutemov.name Link: https://lkml.kernel.org/r/20251027115636.82382-2-kirill@shutemov.name Signed-off-by: Kiryl Shutsemau Fixes: 6795801366da ("xfs: Support large folios") Reported-by: "Darrick J. Wong" Cc: Al Viro Cc: Baolin Wang Cc: Christian Brauner Cc: Dave Chinner Cc: David Hildenbrand Cc: Hugh Dickins Cc: Johannes Weiner Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Mike Rapoport Cc: Rik van Riel Cc: Shakeel Butt Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Kiryl Shutsemau Signed-off-by: Greg Kroah-Hartman

mm: fix apply_to_existing_page_range()

2025-04-25T08:47:53+00:00

commit a995199384347261bb3f21b2e171fa7f988bd2f8 upstream. In the case of apply_to_existing_page_range(), apply_to_pte_range() is reached with 'create' set to false. When !create, the loop over the PTE page table is broken. apply_to_pte_range() will only move to the next PTE entry if 'create' is true or if the current entry is not pte_none(). This means that the user of apply_to_existing_page_range() will not have 'fn' called for any entries after the first pte_none() in the PTE page table. Fix the loop logic in apply_to_pte_range(). There are no known runtime issues from this, but the fix is trivial enough for stable@ even without a known buggy user. Link: https://lkml.kernel.org/r/20250409094043.1629234-1-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Fixes: be1db4753ee6 ("mm/memory.c: add apply_to_existing_page_range() helper") Cc: Daniel Axtens Cc: David Hildenbrand Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

x86/mm/pat: Fix VM_PAT handling when fork() fails in copy_page_range()

2025-04-10T12:39:18+00:00

[ Upstream commit dc84bc2aba85a1508f04a936f9f9a15f64ebfb31 ] If track_pfn_copy() fails, we already added the dst VMA to the maple tree. As fork() fails, we'll cleanup the maple tree, and stumble over the dst VMA for which we neither performed any reservation nor copied any page tables. Consequently untrack_pfn() will see VM_PAT and try obtaining the PAT information from the page table -- which fails because the page table was not copied. The easiest fix would be to simply clear the VM_PAT flag of the dst VMA if track_pfn_copy() fails. However, the whole thing is about "simply" clearing the VM_PAT flag is shaky as well: if we passed track_pfn_copy() and performed a reservation, but copying the page tables fails, we'll simply clear the VM_PAT flag, not properly undoing the reservation ... which is also wrong. So let's fix it properly: set the VM_PAT flag only if the reservation succeeded (leaving it clear initially), and undo the reservation if anything goes wrong while copying the page tables: clearing the VM_PAT flag after undoing the reservation. Note that any copied page table entries will get zapped when the VMA will get removed later, after copy_page_range() succeeded; as VM_PAT is not set then, we won't try cleaning VM_PAT up once more and untrack_pfn() will be happy. Note that leaving these page tables in place without a reservation is not a problem, as we are aborting fork(); this process will never run. A reproducer can trigger this usually at the first try: https://gitlab.com/davidhildenbrand/scratchspace/-/raw/main/reproducers/pat_fork.c WARNING: CPU: 26 PID: 11650 at arch/x86/mm/pat/memtype.c:983 get_pat_info+0xf6/0x110 Modules linked in: ... CPU: 26 UID: 0 PID: 11650 Comm: repro3 Not tainted 6.12.0-rc5+ #92 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014 RIP: 0010:get_pat_info+0xf6/0x110 ... Call Trace: ... untrack_pfn+0x52/0x110 unmap_single_vma+0xa6/0xe0 unmap_vmas+0x105/0x1f0 exit_mmap+0xf6/0x460 __mmput+0x4b/0x120 copy_process+0x1bf6/0x2aa0 kernel_clone+0xab/0x440 __do_sys_clone+0x66/0x90 do_syscall_64+0x95/0x180 Likely this case was missed in: d155df53f310 ("x86/mm/pat: clear VM_PAT if copy_p4d_range failed") ... and instead of undoing the reservation we simply cleared the VM_PAT flag. Keep the documentation of these functions in include/linux/pgtable.h, one place is more than sufficient -- we should clean that up for the other functions like track_pfn_remap/untrack_pfn separately. Fixes: d155df53f310 ("x86/mm/pat: clear VM_PAT if copy_p4d_range failed") Fixes: 2ab640379a0a ("x86: PAT: hooks in generic vm code to help archs to track pfnmap regions - v3") Reported-by: xingwei lee Reported-by: yuxin wang Reported-by: Marius Fleischer Signed-off-by: David Hildenbrand Signed-off-by: Ingo Molnar Cc: Andy Lutomirski Cc: Peter Zijlstra Cc: Rik van Riel Cc: "H. Peter Anvin" Cc: Linus Torvalds Cc: Andrew Morton Cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/20250321112323.153741-1-david@redhat.com Closes: https://lore.kernel.org/lkml/CABOYnLx_dnqzpCW99G81DmOr+2UzdmZMk=T3uxwNxwz+R1RAwg@mail.gmail.com/ Closes: https://lore.kernel.org/lkml/CAJg=8jwijTP5fre8woS4JVJQ8iUA6v+iNcsOgtj9Zfpc3obDOQ@mail.gmail.com/ Signed-off-by: Sasha Levin

lockdep/mm: Fix might_fault() lockdep check of current->mm->mmap_lock

2025-04-10T12:39:11+00:00

[ Upstream commit a1b65f3f7c6f7f0a08a7dba8be458c6415236487 ] Turns out that this commit, about 10 years ago: 9ec23531fd48 ("sched/preempt, mm/fault: Trigger might_sleep() in might_fault() with disabled pagefaults") ... accidentally (and unnessecarily) put the lockdep part of __might_fault() under CONFIG_DEBUG_ATOMIC_SLEEP=y. This is potentially notable because large distributions such as Ubuntu are running with !CONFIG_DEBUG_ATOMIC_SLEEP. Restore the debug check. [ mingo: Update changelog. ] Fixes: 9ec23531fd48 ("sched/preempt, mm/fault: Trigger might_sleep() in might_fault() with disabled pagefaults") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Cc: Linus Torvalds Cc: Andrew Morton Link: https://lore.kernel.org/r/20241104135517.536628371@infradead.org Signed-off-by: Sasha Levin

mm: fix finish_fault() handling for large folios

2025-03-13T12:01:59+00:00

commit 34b82f33cf3f03bc39e9a205a913d790e1520ade upstream. When handling faults for anon shmem finish_fault() will attempt to install ptes for the entire folio. Unfortunately if it encounters a single non-pte_none entry in that range it will bail, even if the pte that triggered the fault is still pte_none. When this situation happens the fault will be retried endlessly never making forward progress. This patch fixes this behavior and if it detects that a pte in the range is not pte_none it will fall back to setting a single pte. [bgeffon@google.com: tweak whitespace] Link: https://lkml.kernel.org/r/20250227133236.1296853-1-bgeffon@google.com Link: https://lkml.kernel.org/r/20250226162341.915535-1-bgeffon@google.com Fixes: 43e027e41423 ("mm: memory: extend finish_fault() to support large folio") Signed-off-by: Brian Geffon Suggested-by: Baolin Wang Reported-by: Marek Maslanka Cc: Hugh Dickins Cc: David Hildenbrand Cc: Hugh Dickens Cc: Kefeng Wang Cc: Matthew Wilcow (Oracle) Cc: Suren Baghdasaryan Cc: Zi Yan Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: don't skip arch_sync_kernel_mappings() in error paths

2025-03-13T12:01:59+00:00

commit 3685024edd270f7c791f993157d65d3c928f3d6e upstream. Fix callers that previously skipped calling arch_sync_kernel_mappings() if an error occurred during a pgtable update. The call is still required to sync any pgtable updates that may have occurred prior to hitting the error condition. These are theoretical bugs discovered during code review. Link: https://lkml.kernel.org/r/20250226121610.2401743-1-ryan.roberts@arm.com Fixes: 2ba3e6947aed ("mm/vmalloc: track which page-table levels were modified") Fixes: 0c95cba49255 ("mm: apply_to_pte_range warn and fail if a large pte is encountered") Signed-off-by: Ryan Roberts Reviewed-by: Anshuman Khandual Reviewed-by: Catalin Marinas Cc: Christop Hellwig Cc: "Uladzislau Rezki (Sony)" Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: use aligned address in copy_user_gigantic_page()

2024-12-27T13:02:20+00:00

commit f5d09de9f1bf9674c6418ff10d0a40cfe29268e1 upstream. In current kernel, hugetlb_wp() calls copy_user_large_folio() with the fault address. Where the fault address may be not aligned with the huge page size. Then, copy_user_large_folio() may call copy_user_gigantic_page() with the address, while copy_user_gigantic_page() requires the address to be huge page size aligned. So, this may cause memory corruption or information leak, addtional, use more obvious naming 'addr_hint' instead of 'addr' for copy_user_gigantic_page(). Link: https://lkml.kernel.org/r/20241028145656.932941-2-wangkefeng.wang@huawei.com Fixes: 530dd9926dc1 ("mm: memory: improve copy_user_large_folio()") Signed-off-by: Kefeng Wang Reviewed-by: David Hildenbrand Cc: Huang Ying Cc: Matthew Wilcox (Oracle) Cc: Muchun Song Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: use aligned address in clear_gigantic_page()

2024-12-27T13:02:20+00:00

commit 8aca2bc96c833ba695ede7a45ad7784c836a262e upstream. In current kernel, hugetlb_no_page() calls folio_zero_user() with the fault address. Where the fault address may be not aligned with the huge page size. Then, folio_zero_user() may call clear_gigantic_page() with the address, while clear_gigantic_page() requires the address to be huge page size aligned. So, this may cause memory corruption or information leak, addtional, use more obvious naming 'addr_hint' instead of 'addr' for clear_gigantic_page(). Link: https://lkml.kernel.org/r/20241028145656.932941-1-wangkefeng.wang@huawei.com Fixes: 78fefd04c123 ("mm: memory: convert clear_huge_page() to folio_zero_user()") Signed-off-by: Kefeng Wang Reviewed-by: "Huang, Ying" Reviewed-by: David Hildenbrand Cc: Matthew Wilcox (Oracle) Cc: Muchun Song Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman

mm: avoid unconditional one-tick sleep when swapcache_prepare fails

2024-10-29T04:40:41+00:00

Commit 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") introduced an unconditional one-tick sleep when `swapcache_prepare()` fails, which has led to reports of UI stuttering on latency-sensitive Android devices. To address this, we can use a waitqueue to wake up tasks that fail `swapcache_prepare()` sooner, instead of always sleeping for a full tick. While tasks may occasionally be woken by an unrelated `do_swap_page()`, this method is preferable to two scenarios: rapid re-entry into page faults, which can cause livelocks, and multiple millisecond sleeps, which visibly degrade user experience. Oven's testing shows that a single waitqueue resolves the UI stuttering issue. If a 'thundering herd' problem becomes apparent later, a waitqueue hash similar to `folio_wait_table[PAGE_WAIT_TABLE_SIZE]` for page bit locks can be introduced. [v-songbaohua@oppo.com: wake_up only when swapcache_wq waitqueue is active] Link: https://lkml.kernel.org/r/20241008130807.40833-1-21cnbao@gmail.com Link: https://lkml.kernel.org/r/20240926211936.75373-1-21cnbao@gmail.com Fixes: 13ddaf26be32 ("mm/swap: fix race when skipping swapcache") Signed-off-by: Barry Song Reported-by: Oven Liyang Tested-by: Oven Liyang Cc: Kairui Song Cc: "Huang, Ying" Cc: Yu Zhao Cc: David Hildenbrand Cc: Chris Li Cc: Hugh Dickins Cc: Johannes Weiner Cc: Matthew Wilcox (Oracle) Cc: Michal Hocko Cc: Minchan Kim Cc: Yosry Ahmed Cc: SeongJae Park Cc: Kalesh Singh Cc: Suren Baghdasaryan Cc: Signed-off-by: Andrew Morton

mm: fix follow_pfnmap API lockdep assert

2024-10-18T16:50:05+00:00

The lockdep asserts for the new follow_pfnmap() API "knows" that a pfnmap always has a vma->vm_file, since that's the only way to create such a mapping. And that's actually true for all the normal cases. But not for the mmap failure case, where the incomplete mapping is torn down and we have cleared vma->vm_file because the failure occured before the file was linked to the vma. So this codepath does actually need to check for vm_file being NULL. Reported-by: Jann Horn Fixes: 6da8e9634bb7 ("mm: new follow_pfnmap API") Cc: Peter Xu Cc: Andrew Morton Signed-off-by: Linus Torvalds