Re: [PATCH v8 4/9] mm: introduce memfd_secret system call to create "secret" memory areas
flat view
From: Mike Rapoport <rppt@kernel.org>
Date: 2020-11-15 08:54:43
Also in:
linux-arch, linux-arm-kernel, linux-fsdevel, linux-kselftest, linux-mm, linux-riscv, lkml, nvdimm
On Fri, Nov 13, 2020 at 01:58:48PM +0000, Matthew Wilcox wrote:
On Tue, Nov 10, 2020 at 05:14:39PM +0200, Mike Rapoport wrote:quoted
+static vm_fault_t secretmem_fault(struct vm_fault *vmf) +{ + struct address_space *mapping = vmf->vma->vm_file->f_mapping; + struct inode *inode = file_inode(vmf->vma->vm_file); + pgoff_t offset = vmf->pgoff; + unsigned long addr; + struct page *page; + int ret = 0; + + if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) + return vmf_error(-EINVAL); + + page = find_get_entry(mapping, offset);Why did you decide to use find_get_entry() here? You don't handle swap or shadow entries.
Right, I've missed that.
quoted
+ if (!page) { + page = secretmem_alloc_page(vmf->gfp_mask); + if (!page) + return vmf_error(-EINVAL);Why is this EINVAL and not ENOMEM?
Ah, I was annoyed by OOMs I got when I simulated various allocation failures, so I changed it to get SIGBUS instead and than forgot to restore. Will fix.
quoted
+ ret = add_to_page_cache(page, mapping, offset, vmf->gfp_mask); + if (unlikely(ret)) + goto err_put_page; + + ret = set_direct_map_invalid_noflush(page, 1); + if (ret) + goto err_del_page_cache; + + addr = (unsigned long)page_address(page); + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); + + __SetPageUptodate(page); + + ret = VM_FAULT_LOCKED; + } + + vmf->page = page; + return ret;Does sparse not warn you about this abuse of vm_fault_t? Separate out 'ret' and 'err'.
Will fix.
quoted hunk ↗ jump to hunk
Andrew, please fold in this fix. I suspect Mike will want to fix the other things I mention above.diff --git a/mm/secretmem.c b/mm/secretmem.c index 3dfdbd85ba00..09ca27f21661 100644 --- a/mm/secretmem.c +++ b/mm/secretmem.c@@ -172,7 +172,7 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf) if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode)) return vmf_error(-EINVAL); - page = find_get_entry(mapping, offset); + page = find_get_page(mapping, offset); if (!page) { page = secretmem_alloc_page(ctx, vmf->gfp_mask); if (!page)
-- Sincerely yours, Mike.