From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f199.google.com (mail-oi1-f199.google.com [209.85.167.199]) (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 83BD74E1C8D for ; Wed, 16 Sep 2026 23:23:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789601008; cv=none; b=Lcxxs1uIczUw6lU9uRGyEe6Bp9TvqJy4UMa4W13Ji7yOFKpxELEOmA6dCJfGS8UGArh42uCr/D7zUnBRktkE+DJLh7+zhdmFBauhoSaJ4a7CY+ED1MHW3d87s+99k06e+huCAPnH77R4fb7S7Z9M1fZ6oF+B+vy/wYABjy6dqe8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789601008; c=relaxed/simple; bh=FnVCxfJ6AJJ+Urfzm5Th794i/GZyUKsidJkmO59nFqs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Xi/bFEipYk+t5nYI3oYlz6IkbgQkCLXRG5sZ7qcomVL1lY+JDimLCQR1bnHCwlfPfszUP3qRMTreKT6CYT00RDRDuU3OrHGdU1OeHFI9e2rWhMBHnt8Jqt9tgIDkBHCejQ2NCrJgkfGPcGR/2lazqUIj3HKJfR9sSytIQmeawKk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--avagin.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=EX2vFoII; arc=none smtp.client-ip=209.85.167.199 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--avagin.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="EX2vFoII" Received: by mail-oi1-f199.google.com with SMTP id 5614622812f47-4ab4ca7ce3fso344398b6e.0 for ; Wed, 16 Sep 2026 16:23:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789601005; x=1790205805; darn=lists.linux.dev; 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=yzKowJpenJDD2vnwNvQsJP6Hsd/QTiS0cw1NoTxC6s8=; b=EX2vFoIIutRAu/s+rSgqtMor4b8KeM1lwo9AotS1IjsWw3n/oqRngjaUqqOO8vcSk6 ncXpU77P0gnnMzKMq5Vko1CUn2yvTg0R1/s6c0wxehqexAhKDz9K3yBxKVJWZqgUtoUf ZSlWpRiMYCX4I9MUdGvCaG89hKubt99femzFdGLNHNAFdOSEtJIG7JngRMTQYgo/Zutl oA0/iaeaAAnQvfZyJIy+nrBAUkBAQOwfWt97GsdAAuoqhmNg4gU3a9VmdjmjWYzMjFqU A3lIEhCA1sxZKsL+DtYQ/rQmFFfgxZfYZLzdyCcIJfvKk0OOxcXxt4bjlQLSfC5bnOfj OrTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789601005; x=1790205805; 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=yzKowJpenJDD2vnwNvQsJP6Hsd/QTiS0cw1NoTxC6s8=; b=C5JAqOs2CDQuZXEhFTcFUdJBqK4wDawV4ip4xpIU9JosQ77IJQgpQOaktsPJ4mUhr4 AOl5vwLv+n3RMd6ydS6sz2a5KBRB0ofpwWqIbUPMYpxM09wt84g04GwDj3zEoO0Xap76 /QgNRXE9eET+4hztRAt6Tm2AS1gLmj3Doo5EzkgdhF+xaR6v6AuOb/Vvnnxi9VXake8l O4Vt0Lo6tJk1K7giIBJw5loEB5MFDWQ3lsb72SJ0R0jgIq3BCihSoz8BOU9dsEzLHztk wVzfkwmJpHTOT7ICYLj8Ieo6GF5GS+1KjNy+TfOMHP4G4ekt1Fi0UYnXoavy5AP31sj/ NrsQ== X-Forwarded-Encrypted: i=1; AKwUvBx1zxwDVw6kBtBXNUhMfT8rSC/Cnasbh8mPNqFGiddHkZ4sj7S7xMvYE6TJC+ZyBrHLKKXf@lists.linux.dev X-Gm-Message-State: AFuF++kt5mPOj6GhoIfmEMC0/C1KmxcXFG5gmenpEZnsKEQeQNG7H5nD TUzs6BicRjm/QpP06mZzaLmFIY57pJxTolH371KnZr9TQJVZExuWlJLbKYs0RG20pX9HEi79bxA MX7cipg== X-Received: from iocrb2-n2.prod.google.com ([2002:a05:6602:a582:20b0:9c3:e4c4:13e1]) (user=avagin job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6808:4fca:b0:4b9:a829:f00e with SMTP id 5614622812f47-4ca4bc74200mr5323830b6e.26.1789601004909; Wed, 16 Sep 2026 16:23:24 -0700 (PDT) Date: Wed, 16 Sep 2026 23:23:08 +0000 In-Reply-To: <20260916232310.490786-1-avagin@google.com> Precedence: bulk X-Mailing-List: criu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260916232310.490786-1-avagin@google.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Message-ID: <20260916232310.490786-6-avagin@google.com> Subject: [PATCH 5/7] x86/fpu: Fix potential underflow in xstate_calculate_size() From: Andrei Vagin To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "Chang S. Bae" Cc: linux-kernel@vger.kernel.org, criu@lists.linux.dev, Dave Hansen , x86@kernel.org, Andrei Vagin , Alexander Mikhalitsyn , "H. Peter Anvin" Content-Type: text/plain; charset="UTF-8" xstate_calculate_size() calculates the size required for a given set of xfeatures. It determines the topmost feature by finding the most significant bit in xfeatures using fls64(xfeatures) - 1. If xfeatures is 0, fls64(0) returns 0, and topmost becomes -1. Previously, topmost was unsigned int, so -1 underflowed to UINT_MAX. This caused the subsequent check `topmost <= XFEATURE_SSE` to fail, and the code proceeded to access xstate arrays using topmost (UINT_MAX) as an index, leading to an out-of-bounds access. Fix this by checking if xfeatures only contains legacy features (FP/SSE) or is empty (!(xfeatures & ~XFEATURE_MASK_FPSSE)) before calculating topmost. Fixes: d6d6d50f1e80 ("x86/fpu/xstate: Consolidate size calculations") Reviewed-by: Alexander Mikhalitsyn Reviewed-by: Chang S. Bae Signed-off-by: Andrei Vagin --- arch/x86/kernel/fpu/xstate.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 3e7f5fb5bfaf..362df13a88cf 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -589,12 +589,13 @@ static bool __init check_xstate_against_struct(int nr) unsigned int xstate_calculate_size(u64 xfeatures, bool compacted) { - unsigned int topmost = fls64(xfeatures) - 1; - unsigned int offset, i; + unsigned int topmost, offset, i; - if (topmost <= XFEATURE_SSE) + if (!(xfeatures & ~XFEATURE_MASK_FPSSE)) return sizeof(struct xregs_state); + topmost = fls64(xfeatures) - 1; + if (compacted) { offset = xfeature_get_offset(xfeatures, topmost); } else { -- 2.55.0.1082.g2b9226bbc0-goog