From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f198.google.com (mail-pl1-f198.google.com [209.85.214.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6197D476CC3 for ; Wed, 26 Aug 2026 16:52:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787763135; cv=none; b=h98Wu8GFgpuzwAiuj5wM+awaHRHVuc6oCl4ijCBTFy6vAabxqiv9MVXsB9jUX1qEV9S92J7CMux4dZ48Iuy3RySsSxNouRwww1Em3f8a7jvi93fGistpcfdma8NUeMJGPWBo67aBCl7C+SlxI/Mi1IbAfwuRVd8e8O53XOsiGOw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787763135; c=relaxed/simple; bh=lKL1AghctyCGhVmrYRZl2IF+lI9RwXIRk4VVRCcz1F8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=tUhsswwuO3UXCaILaENgHCJ9LX94Bpo/4IHGI/dyFpt+GqasFjppyJ5sgbGc3bMQFBW6QA4vOL1WP/Ss6Q5a2z9K0tvKIMCU+TdfgLtJnoX7FXMKDgXcp3Wr+Aq+f3KmVpQQBX9D/x3ecjbE/b+5xsRS9/tUmo4/EwtSgp1lc8c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=dpSqoV3V; arc=none smtp.client-ip=209.85.214.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="dpSqoV3V" Received: by mail-pl1-f198.google.com with SMTP id d9443c01a7336-2d6f73d0f89so17410295ad.0 for ; Wed, 26 Aug 2026 09:52:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1787763118; x=1788367918; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:reply-to:from:to:cc:subject:date:message-id :reply-to:content-type; bh=kih6Ze+eAUyI9b/QVGz2Gk+Uahj8e0YRoP4YxZwC+sQ=; b=dpSqoV3Vw2dujGkjL4hoK2yFYxAzyLYpmodQH/zWzlhFH8nB6xZwQcvdagISuqCrV9 7ea8/hjlhPbZQ0z4WU+IkT+x72i0MommvziCDu+JWq1Qqzs7g7gzHKRC1y7CeL5gLI11 nXUNZ0rrz9CrJp9vxTmSmN/rRh4lRhQfHjtWfIJr8Y9kEQz6QVDAsZHpPHwPUQumAFG9 ZT55FT4JPxgjgu17ec6Fv3SOoiBm0PeN4+nx09R0zS0yxNDNP7WYpQjj6DjBbq1bqn4u RPEMmChmiZcY6znaOd4yemm/5A/wd+1mCG+VHXoRHWKPrgNd6grg71syJB0pVPTKcW05 kONQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1787763118; x=1788367918; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:reply-to:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to:content-type; bh=kih6Ze+eAUyI9b/QVGz2Gk+Uahj8e0YRoP4YxZwC+sQ=; b=Q+RQo8yMdl7GdfNtu6DHfoFgz5MRPauD2aQSPDHAytcp26K4wo2GNjWhXsWsq2WO0Z /noNxvJc98iQpaiBpzako3fL715ouQnSs7s+qvJxiDwt3ubgmrJlgtQMc1/ib4L9Fme5 Hk0z2MKqmWx/vRu2V3Y0Pb2O7ZImHonG95lXU6HyMHlF3jdZatKmCAmPrBBfbfok4wMC 6k2SaKvzhoa7sI8inYAC6pXhV2Zfpqy6+gwushiZar7WTMje1KtrhCMMiymbIce4AlBo mNpwsJpKPnKKQUJN+GP2eo+yViKzcN6rnZqjZoCSLIpCQbOgVA/KV5EaYaZWNPJSuTrA 02sQ== X-Forwarded-Encrypted: i=1; AHgh+RpBdQ1/sdbAosnsxJX4AKfgbtmN3kwMcuxcCPgO7Vz8a0+fXrC9pCmhKGo6TUj7Mv5gRYY=@vger.kernel.org X-Gm-Message-State: AFuF++kflQeHEQ1Cm56TvWbF6Noo9AIGyjOlz17einsPE2NyUGO+n8BH 7CAUxZ5WgsKVnklaCMkmFd9ivmb7AjsFXDBnSbUoJCXD2ZJbAqySMabJlf7uMOaTVrdLZBNxY2f wRrOZAg== X-Received: from plgf9.prod.google.com ([2002:a17:902:ce89:b0:2ca:5a0f:d0c4]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:d4c3:b0:2b2:67ca:5ff9 with SMTP id d9443c01a7336-2d707803e2bmr127600385ad.0.1787763117519; Wed, 26 Aug 2026 09:51:57 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 26 Aug 2026 09:51:53 -0700 In-Reply-To: <20260826165154.766699-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260826165154.766699-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.887.g758fc8c411-goog Message-ID: <20260826165154.766699-2-seanjc@google.com> Subject: [PATCH 1/2] KVM: guest_memfd: Gracefully handle xarray errors when binding a memslot From: Sean Christopherson To: Paolo Bonzini , Sean Christopherson Cc: David Hildenbrand , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Stefan Teodorescu , Dennis Tighe , Sashiko Bot , Yan Zhao Content-Type: text/plain; charset="UTF-8" If inserting a memslot into a guest_memfd's bindings xarray fails, propagate the error back to the caller, i.e. fail memslot creation as well. Signalling success and continuing on with memslot creation results in use-after-free, as the guest_memfd instance will remain reachable via the memslot after the file is freed (kvm_gmem_release() won't nullify the file pointer due to lack of a valid binding). Opportunistically WARN and reject binding if KVM_MEMSLOT_GMEM_ONLY is already set, partly to guard against goofs elsewhere, but mostly so that KVM doesn't need to worry about clobbering flags when unwinding on failure. Fixes: a7800aa80ea4 ("KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory") Cc: stable@vger.kernel.org Reported-by: Stefan Teodorescu Reported-by: Dennis Tighe Reported-by: Sashiko Bot Closes: https://lore.kernel.org/all/20260823135031.4F6DC1F000E9%40smtp.kernel.org Signed-off-by: Sean Christopherson --- virt/kvm/guest_memfd.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index b596486d184c..1ef9e2916423 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -612,10 +612,14 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, struct inode *inode; struct file *file; int r = -EINVAL; + void *xar; BUILD_BUG_ON(sizeof(gpa_t) != sizeof(offset)); BUILD_BUG_ON(sizeof(gfn_t) != sizeof(slot->gmem.pgoff)); + if (WARN_ON_ONCE(slot->flags & KVM_MEMSLOT_GMEM_ONLY)) + return -EINVAL; + file = fget(fd); if (!file) return -EBADF; @@ -654,7 +658,7 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, if (kvm_gmem_supports_mmap(inode)) slot->flags |= KVM_MEMSLOT_GMEM_ONLY; - xa_store_range(&f->bindings, start, end - 1, slot, GFP_KERNEL); + xar = xa_store_range(&f->bindings, start, end - 1, slot, GFP_KERNEL); filemap_invalidate_unlock(inode->i_mapping); /* @@ -662,7 +666,12 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, * not the other way 'round. Active bindings are invalidated if the * file is closed before memslots are destroyed. */ - r = 0; + r = xa_is_err(xar) ? xa_err(xar) : 0; + if (r) { + slot->gmem.file = NULL; + slot->gmem.pgoff = 0; + slot->flags &= ~KVM_MEMSLOT_GMEM_ONLY; + } err: fput(file); return r; -- 2.55.0.887.g758fc8c411-goog