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Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , tarunsahu@google.com, Jason Gunthorpe , Vlastimil Babka , Baoquan He Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, Ackerley Tng , Xiaoyao Li X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1786139565; l=2563; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=yJn/ZHgiLozpfiaF3WvTX3dAxLUI4g7cee7UK9m2PVM=; b=l30Jr9f3hi6OTXNRNCJUYvIodwuNAe/9sIlpUlyIylb9JLbckvWkQEC0O3MkF9z/Ad2RJAuKg fQ+UqUROtkeAcqmpEqLAFhsm4pcVQLQgS28LhNijkgBlq/BTWV7VOub X-Developer-Key: i=ackerleytng@google.com; a=ed25519; pk=sAZDYXdm6Iz8FHitpHeFlCMXwabodTm7p8/3/8xUxuU= X-Endpoint-Received: by B4 Relay for ackerleytng@google.com/20260225 with auth_id=649 X-Original-From: Ackerley Tng Reply-To: ackerleytng@google.com X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B9AFC1C0007 X-Rspam-User: X-Stat-Signature: z1ofmwhr4ebpnrhtget9dzu4sf8t8euw X-HE-Tag: 1786139575-504364 X-HE-Meta: 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 4nMf2kx6 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Ackerley Tng Move the folio initialization logic from kvm_gmem_get_pfn() into __kvm_gmem_get_pfn() to also zero pages if the page is to be used in kvm_gmem_populate(). With in-place conversion, the existing data in a guest_memfd page can be populated into guest memory through platform-specific ioctls. Without first zeroing the page obtained using __kvm_gmem_get_pfn(), it might contain uninitialized host memory, which would leak to the guest if the populate completes. guest_memfd pages are zeroed at most once in the page's entire lifetime with guest_memfd, and that is tracked using the uptodate flag. Zeroing the page in __kvm_gmem_get_pfn() is chosen over zeroing in kvm_gmem_get_folio() since other flows, such as a future write() syscall, can get a page, write to the page and then set page uptodate without zeroing. This aligns with the concept of zeroing before first use - the other place where zeroing happens is in kvm_gmem_fault_user_mapping(). Don't mark the page uptodate again after populating, since the page would already be marked uptodate before the post_populate() call. Reviewed-by: Fuad Tabba Tested-by: Shivank Garg Reviewed-by: Xiaoyao Li Signed-off-by: Ackerley Tng --- virt/kvm/guest_memfd.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 030af0855f8b0..41950c8105b5d 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -1079,6 +1079,11 @@ static struct folio *__kvm_gmem_get_pfn(struct file *file, return ERR_PTR(-EHWPOISON); } + if (!folio_test_uptodate(folio)) { + clear_highpage(folio_page(folio, 0)); + folio_mark_uptodate(folio); + } + *pfn = folio_file_pfn(folio, index); if (max_order) *max_order = 0; @@ -1108,11 +1113,6 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, goto out; } - if (!folio_test_uptodate(folio)) { - clear_highpage(folio_page(folio, 0)); - folio_mark_uptodate(folio); - } - #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT if (kvm_gmem_is_private_mem(file_inode(file), index)) r = kvm_arch_gmem_make_private(kvm, gfn, *pfn, @@ -1159,8 +1159,6 @@ static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot, } ret = post_populate(kvm, gfn, pfn, src_page, opaque); - if (!ret) - folio_mark_uptodate(folio); out_put_folio: folio_put(folio); -- 2.55.0.654.g21b8a5bc05-goog