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Shutemov" , Mike Kravetz , Minchan Kim , Russell King , Thomas Bogendoerfer , Thomas Gleixner , Vishal Verma , Vlastimil Babka , Will Deacon , linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 2/6] mm/mremap: For MREMAP_DONTUNMAP check security_vm_enough_memory_mm() Date: Tue, 13 Oct 2020 02:34:12 +0100 Message-Id: <20201013013416.390574-3-dima@arista.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201013013416.390574-1-dima@arista.com> References: <20201013013416.390574-1-dima@arista.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Currently memory is accounted post-mremap() with MREMAP_DONTUNMAP, which may break overcommit policy. So, check if there's enough memory before doing actual VMA copy. Don't unset VM_ACCOUNT on MREMAP_DONTUNMAP. By semantics, such mremap() is actually a memory allocation. That also simplifies the error-path a little. Also, as it's memory allocation on success don't reset hiwater_vm value. Fixes: commit e346b3813067 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()"= ) Signed-off-by: Dmitry Safonov --- mm/mremap.c | 36 +++++++++++++----------------------- 1 file changed, 13 insertions(+), 23 deletions(-) diff --git a/mm/mremap.c b/mm/mremap.c index 03d31a0d4c67..c248f9a52125 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -365,11 +365,19 @@ static unsigned long move_vma(struct vm_area_struct= *vma, if (err) return err; =20 + if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) { + if (security_vm_enough_memory_mm(mm, new_len >> PAGE_SHIFT)) + return -ENOMEM; + } + new_pgoff =3D vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT= ); new_vma =3D copy_vma(&vma, new_addr, new_len, new_pgoff, &need_rmap_locks); - if (!new_vma) + if (!new_vma) { + if (unlikely(flags & MREMAP_DONTUNMAP && vm_flags & VM_ACCOUNT)) + vm_unacct_memory(new_len >> PAGE_SHIFT); return -ENOMEM; + } =20 moved_len =3D move_page_tables(vma, old_addr, new_vma, new_addr, old_le= n, need_rmap_locks); @@ -398,7 +406,7 @@ static unsigned long move_vma(struct vm_area_struct *= vma, } =20 /* Conceal VM_ACCOUNT so old reservation is not undone */ - if (vm_flags & VM_ACCOUNT) { + if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) { vma->vm_flags &=3D ~VM_ACCOUNT; excess =3D vma->vm_end - vma->vm_start - old_len; if (old_addr > vma->vm_start && @@ -423,34 +431,16 @@ static unsigned long move_vma(struct vm_area_struct= *vma, untrack_pfn_moved(vma); =20 if (unlikely(!err && (flags & MREMAP_DONTUNMAP))) { - if (vm_flags & VM_ACCOUNT) { - /* Always put back VM_ACCOUNT since we won't unmap */ - vma->vm_flags |=3D VM_ACCOUNT; - - vm_acct_memory(new_len >> PAGE_SHIFT); - } - - /* - * VMAs can actually be merged back together in copy_vma - * calling merge_vma. This can happen with anonymous vmas - * which have not yet been faulted, so if we were to consider - * this VMA split we'll end up adding VM_ACCOUNT on the - * next VMA, which is completely unrelated if this VMA - * was re-merged. - */ - if (split && new_vma =3D=3D vma) - split =3D 0; - /* We always clear VM_LOCKED[ONFAULT] on the old vma */ vma->vm_flags &=3D VM_LOCKED_CLEAR_MASK; =20 /* Because we won't unmap we don't need to touch locked_vm */ - goto out; + return new_addr; } =20 if (do_munmap(mm, old_addr, old_len, uf_unmap) < 0) { /* OOM: unable to split vma, just get accounts right */ - if (vm_flags & VM_ACCOUNT) + if (vm_flags & VM_ACCOUNT && !(flags & MREMAP_DONTUNMAP)) vm_acct_memory(new_len >> PAGE_SHIFT); excess =3D 0; } @@ -459,7 +449,7 @@ static unsigned long move_vma(struct vm_area_struct *= vma, mm->locked_vm +=3D new_len >> PAGE_SHIFT; *locked =3D true; } -out: + mm->hiwater_vm =3D hiwater_vm; =20 /* Restore VM_ACCOUNT if one or two pieces of vma left */ --=20 2.28.0