From fdbef61491359947753c13581098878e8d038286 Mon Sep 17 00:00:00 2001 From: Dmitry Safonov Date: Fri, 5 Nov 2021 13:39:06 -0700 Subject: mm/mremap: don't account pages in vma_to_resize() All this vm_unacct_memory(charged) dance seems to complicate the life without a good reason. Furthermore, it seems not always done right on error-pathes in mremap_to(). And worse than that: this `charged' difference is sometimes double-accounted for growing MREMAP_DONTUNMAP mremap()s in move_vma(): if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT)) Let's not do this. Account memory in mremap() fast-path for growing VMAs or in move_vma() for actually moving things. The same simpler way as it's done by vm_stat_account(), but with a difference to call security_vm_enough_memory_mm() before copying/adjusting VMA. Originally noticed by Chen Wandun: https://lkml.kernel.org/r/20210717101942.120607-1-chenwandun@huawei.com Link: https://lkml.kernel.org/r/20210721131320.522061-1-dima@arista.com Fixes: e346b3813067 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()") Signed-off-by: Dmitry Safonov Acked-by: Brian Geffon Cc: Alexander Viro Cc: Andy Lutomirski Cc: Catalin Marinas Cc: Chen Wandun Cc: Dan Carpenter Cc: Dan Williams Cc: Dave Jiang Cc: Hugh Dickins Cc: Ingo Molnar Cc: Jason Gunthorpe Cc: John Hubbard Cc: Kefeng Wang Cc: "Kirill A. Shutemov" Cc: Mike Kravetz Cc: Minchan Kim Cc: Ralph Campbell Cc: Russell King Cc: Thomas Bogendoerfer Cc: Thomas Gleixner Cc: Vishal Verma Cc: Vlastimil Babka Cc: Wei Yongjun Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mremap.c | 50 ++++++++++++++++++++++---------------------------- 1 file changed, 22 insertions(+), 28 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index badfe17ade1f..c0b6c41b7b78 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -565,6 +565,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, bool *locked, unsigned long flags, struct vm_userfaultfd_ctx *uf, struct list_head *uf_unmap) { + long to_account = new_len - old_len; struct mm_struct *mm = vma->vm_mm; struct vm_area_struct *new_vma; unsigned long vm_flags = vma->vm_flags; @@ -583,6 +584,9 @@ static unsigned long move_vma(struct vm_area_struct *vma, if (mm->map_count >= sysctl_max_map_count - 3) return -ENOMEM; + if (unlikely(flags & MREMAP_DONTUNMAP)) + to_account = new_len; + if (vma->vm_ops && vma->vm_ops->may_split) { if (vma->vm_start != old_addr) err = vma->vm_ops->may_split(vma, old_addr); @@ -604,8 +608,8 @@ static unsigned long move_vma(struct vm_area_struct *vma, if (err) return err; - if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) { - if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT)) + if (vm_flags & VM_ACCOUNT) { + if (security_vm_enough_memory_mm(mm, to_account >> PAGE_SHIFT)) return -ENOMEM; } @@ -613,8 +617,8 @@ static unsigned long move_vma(struct vm_area_struct *vma, new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff, &need_rmap_locks); if (!new_vma) { - if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) - vm_unacct_memory(new_len >> PAGE_SHIFT); + if (vm_flags & VM_ACCOUNT) + vm_unacct_memory(to_account >> PAGE_SHIFT); return -ENOMEM; } @@ -708,8 +712,7 @@ static unsigned long move_vma(struct vm_area_struct *vma, } static struct vm_area_struct *vma_to_resize(unsigned long addr, - unsigned long old_len, unsigned long new_len, unsigned long flags, - unsigned long *p) + unsigned long old_len, unsigned long new_len, unsigned long flags) { struct mm_struct *mm = current->mm; struct vm_area_struct *vma; @@ -768,13 +771,6 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr, (new_len - old_len) >> PAGE_SHIFT)) return ERR_PTR(-ENOMEM); - if (vma->vm_flags & VM_ACCOUNT) { - unsigned long charged = (new_len - old_len) >> PAGE_SHIFT; - if (security_vm_enough_memory_mm(mm, charged)) - return ERR_PTR(-ENOMEM); - *p = charged; - } - return vma; } @@ -787,7 +783,6 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, struct mm_struct *mm = current->mm; struct vm_area_struct *vma; unsigned long ret = -EINVAL; - unsigned long charged = 0; unsigned long map_flags = 0; if (offset_in_page(new_addr)) @@ -830,7 +825,7 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, old_len = new_len; } - vma = vma_to_resize(addr, old_len, new_len, flags, &charged); + vma = vma_to_resize(addr, old_len, new_len, flags); if (IS_ERR(vma)) { ret = PTR_ERR(vma); goto out; @@ -853,7 +848,7 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, ((addr - vma->vm_start) >> PAGE_SHIFT), map_flags); if (IS_ERR_VALUE(ret)) - goto out1; + goto out; /* We got a new mapping */ if (!(flags & MREMAP_FIXED)) @@ -862,12 +857,6 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len, ret = move_vma(vma, addr, old_len, new_len, new_addr, locked, flags, uf, uf_unmap); - if (!(offset_in_page(ret))) - goto out; - -out1: - vm_unacct_memory(charged); - out: return ret; } @@ -899,7 +888,6 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, struct mm_struct *mm = current->mm; struct vm_area_struct *vma; unsigned long ret = -EINVAL; - unsigned long charged = 0; bool locked = false; bool downgraded = false; struct vm_userfaultfd_ctx uf = NULL_VM_UFFD_CTX; @@ -981,7 +969,7 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, /* * Ok, we need to grow.. */ - vma = vma_to_resize(addr, old_len, new_len, flags, &charged); + vma = vma_to_resize(addr, old_len, new_len, flags); if (IS_ERR(vma)) { ret = PTR_ERR(vma); goto out; @@ -992,10 +980,18 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, if (old_len == vma->vm_end - addr) { /* can we just expand the current mapping? */ if (vma_expandable(vma, new_len - old_len)) { - int pages = (new_len - old_len) >> PAGE_SHIFT; + long pages = (new_len - old_len) >> PAGE_SHIFT; + + if (vma->vm_flags & VM_ACCOUNT) { + if (security_vm_enough_memory_mm(mm, pages)) { + ret = -ENOMEM; + goto out; + } + } if (vma_adjust(vma, vma->vm_start, addr + new_len, vma->vm_pgoff, NULL)) { + vm_unacct_memory(pages); ret = -ENOMEM; goto out; } @@ -1034,10 +1030,8 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len, &locked, flags, &uf, &uf_unmap); } out: - if (offset_in_page(ret)) { - vm_unacct_memory(charged); + if (offset_in_page(ret)) locked = false; - } if (downgraded) mmap_read_unlock(current->mm); else -- cgit v1.2.3