From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (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 C50F241B357 for ; Mon, 13 Jul 2026 13:14:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783948476; cv=none; b=rJr2ebORgUFD1uo90azUbEKezA1TcMERfiSvtpI8bRTrIW5Tqnqp/Suq0ba8ZZNJohhnGSgev8zlXab7zdxKL9dNCxIPHyyIwcWqqKMdAk7W7NooxZDGM8feudzvk0P7SMPSBT2abM+TMgRyfSOdpJ8+r7vWHz28yJj/W+xO8Ds= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783948476; c=relaxed/simple; bh=Kjq4Pg1RnSNshQ/oIm/A1+YWWa+4x8HogwZlKAKfb3M=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=pOl1nhp+ZiuV+w/A5QYtqWRXt6DJ8kWZHOnFlim0TOe68jSzX5Xnll8u5WTKfzB0JGU1dcpeEnT/3lph6XDx98Wfy5jBc+nX9MA67H1f2fxhwdMRxKEYh3iRCvtSIRoLFpnfereAygrClhylkqbiS7WoKRFK9wxfNQuNB9VqAwI= 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=T6oEVirx; arc=none smtp.client-ip=209.85.210.201 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="T6oEVirx" Received: by mail-pf1-f201.google.com with SMTP id d2e1a72fcca58-8484b9fb055so2087503b3a.0 for ; Mon, 13 Jul 2026 06:14:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1783948474; x=1784553274; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=k6Enmvxk2RO2BuqLZjH3U2On0bHXYN40a1K8A0vvkYc=; b=T6oEVirxrb+uHgd3JtlRQVd2uMvP0qUNsNIYjic6EYtF8N9PDBmb7w/2JvNylVzfyS f+y1uCeEC0IXP62EHLAm+44Mj1dyPinqIhyW3uBG9KN7iNwyz3t/YrdIY+asNrLhx+U1 YGumc6o2/64QGKKOQz+/tZFy2Y+bRwzF8Do/LxdcZW82o4EpZP7ENOADhiQXxpemoIhp B2I61GR9dnxQkw6wevSdofn4qhKGIFJz7hQ8x7uIhtEZ+kRiuo053TnnN58xG3Cc94j6 2xBR2aMPB1mLk4hqNA/QSIZbfQSYwn/kI6AbCpvjcm99u2a+QoJJ6/j9FZUpMAzBJ91N XPpA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783948474; x=1784553274; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=k6Enmvxk2RO2BuqLZjH3U2On0bHXYN40a1K8A0vvkYc=; b=fhFHNWgU0nu3GaBpuCWxTXXSTtOHLKbK4GLhzjzndwYk01Ve4/7HwqIPimopU5sIcn hTh4/7U5Rb3dQNNU8xLUYhS4spr+SpugYVgmZO95Xh89Iq/wFIU9wVk1sY+lEwRVD8ly q3dD8Ec6gKrwHpHsGQLbgLuw9mf99wpU3CG1aOhdg+tAQNeVCCdoGg0/arJ3MUS9ZMAJ 4KPAzUDKARWyak8RA+4Es/HKK+XkQBVCYEkEg91iK2lZZDJtdWsFlQuF2fb7imzSwHKf ma1bfrE8caL00DOG17kqbSfxHQgpVfqhxsbfJJlhPPNENlWwJe/Jp0mo9fIidfqwW+W/ uc0g== X-Forwarded-Encrypted: i=1; AHgh+RqOahLrPEhjp0Euypq1Lg+NdhXsB5jkrzJKcM9f6HdXOINo2EUcXdWfF+MzUzFJnKGreZ1PuNq8mO8aogs=@vger.kernel.org X-Gm-Message-State: AOJu0YyqG0c6A6NuuIWDwkdFca1AX4yIwiK9DIK5gHmIZMl3d5xQjUSm pOzPhgXzg5VX6nvTgjYxgYyw8qpCyQS9W6pETBNHvnUJ/j0/ch3rRxECs90s3oU5g/oh5PFmYYO j4c6AxQ== X-Received: from pfbfo1.prod.google.com ([2002:a05:6a00:6001:b0:848:2c15:fb05]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:2d9e:b0:847:8650:69cd with SMTP id d2e1a72fcca58-84889664234mr8350251b3a.33.1783948473850; Mon, 13 Jul 2026 06:14:33 -0700 (PDT) Date: Mon, 13 Jul 2026 06:14:31 -0700 In-Reply-To: <20260712090039.36038-1-kartikey406@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260712090039.36038-1-kartikey406@gmail.com> Message-ID: Subject: Re: [PATCH] KVM: x86: Handle -1 return from kvm_cpu_get_interrupt From: Sean Christopherson To: Deepanshu Kartikey Cc: pbonzini@redhat.com, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+9dcd0a11dc9703a49511@syzkaller.appspotmail.com Content-Type: text/plain; charset="us-ascii" On Sun, Jul 12, 2026, Deepanshu Kartikey wrote: > kvm_check_and_inject_events() checks for a pending PIC > interrupt using kvm_cpu_has_injectable_intr() and then > fetches it using kvm_cpu_get_interrupt(). These two > operations are not atomic with respect to vpic->output. > > Between the check and fetch, another thread running on > a different CPU can call kvm_pic_read_irq() which sets > output=0 before taking pic_lock(), making it immediately > visible to all other threads: > > Thread A: kvm_cpu_has_injectable_intr() reads output=1 > Thread B: kvm_pic_read_irq() sets output=0 before lock > Thread A: kvm_cpu_get_interrupt() reads output=0 > Thread A: returns -1, WARN_ON_ONCE fires > > The -1 return is a valid result indicating another thread > already consumed the interrupt between the check and fetch. > Replace WARN_ON_ONCE with a graceful goto out to handle > this race condition correctly. > > Reported-by: syzbot+9dcd0a11dc9703a49511@syzkaller.appspotmail.com > Link: https://syzkaller.appspot.com/bug?extid=9dcd0a11dc9703a49511 Already being handled, thanks! https://lore.kernel.org/all/86078441-92eb-4461-b823-7d3539ac5859@mail.kernel.org