From: Jann Horn jannh@google.com

stable inclusion from stable-v4.19.257 commit c3b1e88f14e7f442e2ddcbec94527eec84ac0ca3 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5PE9S CVE: CVE-2022-39188

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commit b67fbebd4cf980aecbcc750e1462128bffe8ae15 upstream.

Some drivers rely on having all VMAs through which a PFN might be accessible listed in the rmap for correctness. However, on X86, it was possible for a VMA with stale TLB entries to not be listed in the rmap.

This was fixed in mainline with commit b67fbebd4cf9 ("mmu_gather: Force tlb-flush VM_PFNMAP vmas"), but that commit relies on preceding refactoring in commit 18ba064e42df3 ("mmu_gather: Let there be one tlb_{start,end}_vma() implementation") and commit 1e9fdf21a4339 ("mmu_gather: Remove per arch tlb_{start,end}_vma()").

This patch provides equivalent protection without needing that refactoring, by forcing a TLB flush between removing PTEs in unmap_vmas() and the call to unlink_file_vma() in free_pgtables().

[This is a stable-specific rewrite of the upstream commit!] Signed-off-by: Jann Horn jannh@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com Reviewed-by: Kefeng Wang wangkefeng.wang@huawei.com Reviewed-by: Xiu Jianfeng xiujianfeng@huawei.com Reviewed-by: zuoze zuoze1@huawei.com Signed-off-by: Yongqiang Liu liuyongqiang13@huawei.com --- mm/mmap.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c index a2699bc10f7b..3bf113a24599 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2899,6 +2899,18 @@ static void unmap_region(struct mm_struct *mm, tlb_gather_mmu(&tlb, mm, start, end); update_hiwater_rss(mm); unmap_vmas(&tlb, vma, start, end); + + /* + * Ensure we have no stale TLB entries by the time this mapping is + * removed from the rmap. + * Note that we don't have to worry about nested flushes here because + * we're holding the mm semaphore for removing the mapping - so any + * concurrent flush in this region has to be coming through the rmap, + * and we synchronize against that using the rmap lock. + */ + if ((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) != 0) + tlb_flush_mmu(&tlb); + free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS, next ? next->vm_start : USER_PGTABLES_CEILING); tlb_finish_mmu(&tlb, start, end);