From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) (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 49ADA44A3EF for ; Wed, 2 Sep 2026 18:20:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788373225; cv=none; b=lXuDEfusLiYEfCk7JeBdNMTIvN1vBXWPKd3wl7//naoEJgfMayvsNrOQSB98Uvp+C2eD4T8OZ3RpTCIWS6Zvd+2AfrYIL5krUVP+OaHkFK577UYeBsdBw0LO4r6pSHzAmZTqwwUH3Uon0SDPqRcASMeCl96Fp0miMOrr0AvoCfI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788373225; c=relaxed/simple; bh=4nM44dji28w11w5Jz6G8Fn8/bMsweabqa4o1j27fvSI=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=E+6QfughsEQWrqfqGR4UKsgQ59atPe1NRiogW/yY0cW5URF/IXax+kskf3jiCE0BHX5eQ+R6AM1AIvI2NrNuL59ZFPEaksK8ZSSfsG6VFiH5ZP6QBEPvE1nxZFzHzF0pa+qefiaOJKCth+WmB46794NjH+Zg9CRenTSpfKQsJwc= 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=hRLkLrhg; arc=none smtp.client-ip=209.85.210.198 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="hRLkLrhg" Received: by mail-pf1-f198.google.com with SMTP id d2e1a72fcca58-8485d853b08so2184948b3a.1 for ; Wed, 02 Sep 2026 11:20:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1788373223; x=1788978023; 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=Ti7lJbGj6xN91aSen76gggEVAHK8aMIWKvWm2Rqm9Hw=; b=hRLkLrhglCKQLv3hOGl4+ipbDsqfaX/CEDWYiZ0EXyPdNSnxtfSJKs8tTyxBkhGver S4Hja+eTvNTr8Z/dQzj+g9nSQb0Jpw6Pi15pLtzpcaRtsnSJrUcPDvAuZVcCI8WZGPGJ AjTRDchhEn9JOj1jpvlWeaRSRyFJknkK7oSw75hARvVZ8sR4lEVfZLD51SpxPZxeZgXI nbPV1ZiQOXx7Sx05HsBc4yDOO/kGg+LQKTDLU5nqMkRJsYknAUqUCMSp0PkYMpY8IARl U8cyU7C4UA6RiBHU7AIovuWjaXNeERjewrdGe4ZKKzF+L+oDsMX5hapHIj+nKwQNEaeJ w5Tg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1788373223; x=1788978023; 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=Ti7lJbGj6xN91aSen76gggEVAHK8aMIWKvWm2Rqm9Hw=; b=hufclOgBoy0I2X0V7Y/kAd1RPjoSpBxTNJXDQ8AQqdmrfIW8wSMdcYM3B0ZtxUI5RP 9A1iCY0htOhUqfuxx7ugJLJaC1/kEScZ0+JoaZTCSId7DdFztKhmwDbqchoIQqCLeTTz 1N2o0tIIjie1K4JLV7wY/wKS2LvSfe2Sju17QoZmvco9+pHcqaaIZH6+mZ2Itb8wvBTq mOcIRR4CTo4G8Semtyqfej75sZg/hARybCkixFnWIFa1q1hPvzWGlQvhdsrtqInkXVXZ eldIg5P9A3jeUv0fSC1m9nfPj8twAbEvJRn9Znp3diNGSWaXCKWUC4KIkkb2sYO8w8D8 m5QQ== X-Forwarded-Encrypted: i=1; AKwUvBwjlEqgcm4X6Iy7K5TsA3/adjXPyC5Vxc8WbsH42xw/QShwow3GJlmYF72kCTAVJLnMOnQ=@vger.kernel.org X-Gm-Message-State: AFuF++n2G5vCnS7vUyt8HPmcCpObH2BSJkY4NjHUM999Tq4I8IxZ2W2p nKAJnQOsTL+RRg/OWkDA8qzp0EVXGS42Gx+zfhhZE58/cdGUcVrbF6RgcmrPP/DlKZ6qeHYlcy7 s9pFSxg== X-Received: from pfwp50.prod.google.com ([2002:a05:6a00:26f2:b0:848:2e0e:62e]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:4298:b0:857:3b70:209 with SMTP id d2e1a72fcca58-85ed1d08cb0mr11287585b3a.1.1788373223333; Wed, 02 Sep 2026 11:20:23 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 2 Sep 2026 11:20:17 -0700 In-Reply-To: <20260902182020.2615443-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260902182020.2615443-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.970.g62bdec98f9-goog Message-ID: <20260902182020.2615443-2-seanjc@google.com> Subject: [PATCH v2 1/4] KVM: guest_memfd: Gracefully handle xarray errors when binding a memslot From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini 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 | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index b596486d184c..2c8d8735de5f 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 +666,13 @@ 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) { + xa_store_range(&f->bindings, start, end - 1, NULL, GFP_KERNEL); + slot->gmem.file = NULL; + slot->gmem.pgoff = 0; + slot->flags &= ~KVM_MEMSLOT_GMEM_ONLY; + } err: fput(file); return r; -- 2.55.0.970.g62bdec98f9-goog