From nobody Fri Dec 19 19:01:38 2025 Received: from mail-pf1-f195.google.com (mail-pf1-f195.google.com [209.85.210.195]) (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 4D15F76026 for ; Tue, 14 Oct 2025 13:02:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.195 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760446939; cv=none; b=TVaPp8iyIS9qX/7QseW4nqNR6hOEg43NqJ6YdYHUD+7N7ZaenfBLtPgXu36xg9vEuZp1OmcpwWMLbtIu9TQGdG9UgfW+ZUMjBLdIyUHB9AQcm9qYZScQ7nAp63uW0BiNtmxQlo4PZDnZ1UYWnjWVjZxnP1WCnkM4rg27GbtDRM0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760446939; c=relaxed/simple; bh=XGY7u+lqhb/sqJLYAZEut8PFrDzJJEOreAKW851JRMQ=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:Content-Type; b=uAZ/FbhdMpc/rTI8E/W/Ds2JLr2Hk9k3K1mQe4yGFaBa5JLjznwxfZANZ/9kImmAwgJ+5y2IHnARKyrUfOZzx5AVU33k+CZGuwLb6ClIuWbd4foKR+vtCKt46+fOKPI+YrWM7ddC7r44MbAFY7DhGOxXbMNRxfKJUGS/uqI0XEo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=UolIS9Rl; arc=none smtp.client-ip=209.85.210.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="UolIS9Rl" Received: by mail-pf1-f195.google.com with SMTP id d2e1a72fcca58-7811fa91774so4568855b3a.0 for ; Tue, 14 Oct 2025 06:02:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1760446937; x=1761051737; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=9vUG8NnvzxTzuqf3xDOLZ/nhw7UAeONEASLUMUFNz60=; b=UolIS9RlZ/Uh0SCZ0OeXi4AqrVUxKgDRf5bzfBm7wVI9slyUihPbfYEvqHaZiBUX7b TVEx1HFvvgkmlEpCPnXzzaTfQ/2Yt3YOPBZSA3FPNhuls/5S09Aq3EH4JFIpadx9KpMG xtxcD4ZlK35cXn0nozTaOzDx5PEa4/Mawho54BoO6OjX0MAK3Q1bDiIfFFUbxezEGX2B gqj9/sdseiJLmL7GZ1aUzQxwKd8ZXUr/p8cBm6TgkjDWHfUGdbVM6Kr0JHB4qrhq3NoH 8ZPdSeQzLVm4itHRlHrbSC+nJ1s41e9tZ9cXRZ0hH2blJBZcs0IqHEuwlcvOJtG6zBim 0RkA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760446937; x=1761051737; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=9vUG8NnvzxTzuqf3xDOLZ/nhw7UAeONEASLUMUFNz60=; b=dKJxdJ5Y9x72QDXD/exB2I7S5AAAQ+sjXnIpMgK4IctiyW2UAP0lDMDaT+NT75oq+L /Yyn/+lNVPZaA1CwL2Lg7zOE+MCiDOKiIXvj+EC6kWj3Z+1DWTo+EHbdVPUvKWlfNpcY MRIcP/RcmqBHX9+GGikrU3NKWVCPv/He8BFPIz4STIQa24GDtpandLARVP7tQPrrlRul C96F8w6Knig2CR8gIMItp86zzFSnXmUsLZ1Ak6QMxLEAnWQTJAQvK21s8PAPT4fGILP1 FhwrXCCNK00fhQxTAJA823wlObzGX0md2SBdXIWQiqh7QKRam9Ez8LiEND1reaCFJYFG YpMQ== X-Forwarded-Encrypted: i=1; AJvYcCV9DWh3pf/eG2WKDux8VcuZl72JzfTzxDpoUlAkO78TPkYfVHZijBUIeMaHUyqetp+R1Y1lvy8BwYSPCzU=@vger.kernel.org X-Gm-Message-State: AOJu0Ywn8lXjCLTH2+yXeHXMolf8lJqeN/JkhdFZw4SKH8oSYTmrROvh a35SvKyNLY/dwiWkfKw9HuKB1uy0Kj3Z2UFLPDIde6PeaIcEqHdKuN5v X-Gm-Gg: ASbGnctDhPR+hSOXm+ZTfiEFm3ZEdZMLT26FqoWhsAWwyM8DrLW7HcfqCqtyIFEHspW C/3T5SBjoilBFtBjczYbU6xqxKrcfDrXf/hwSgtRl/3+8I+RjPbEIelXPuyoss57nG+pmKWiknS 2iVIcC5m77f7k2Iu3KS0W//1BXn1t2xmRT9BC9tTXgbruO9Qv8CsO+2W8Bavx7mspKtKTiw9G+T au4RZptm4/D1KvKcx34h3p+CCvOBBowW0eBC+VOMoKBNMue8QbTOSH+BR1ljOEzCMMBz5wIvK3R NLmQjmNjbiujAaCZEDLjWvRmQwfAEA2vsUoWBDaJVAmyHxa/Mn8yWaA+2lLXU+Ba0HOknjdkMS9 Z5cvIcOb268aUS8pH/Lx/BHOUuka0fwuU3oph X-Google-Smtp-Source: AGHT+IF4gyFwIQTa6KYBIdWHVozU4jIMjBZx4vqsFvot1tX3tYw5PWnT47+yK/5qpppovCPchU7vng== X-Received: by 2002:a05:6a00:1894:b0:776:130f:e1a1 with SMTP id d2e1a72fcca58-79385709579mr28317674b3a.5.1760446937136; Tue, 14 Oct 2025 06:02:17 -0700 (PDT) Received: from OSVS.. ([183.101.168.247]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7992dc86a93sm15012439b3a.75.2025.10.14.06.02.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Oct 2025 06:02:15 -0700 (PDT) From: Jaehun Gou To: Namjae Jeon Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jaehun Gou , Seunghun Han , Jihoon Kwon Subject: [PATCH] fs: exfat: fix improper check of dentry.stream.valid_size Date: Tue, 14 Oct 2025 22:01:46 +0900 Message-ID: <20251014130146.3948175-1-p22gone@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable We found an infinite loop bug in the exFAT file system that can lead to a Denial-of-Service (DoS) condition. When a dentry in an exFAT filesystem is malformed, the following system calls =E2=80=94 SYS_openat, SYS_ftruncate, = and SYS_pwrite64 =E2=80=94 can cause the kernel to hang. Root cause analysis shows that the size validation code in exfat_find() does not check whether dentry.stream.valid_size is negative. As a result, the system calls mentioned above can succeed and eventually trigger the DoS issue. This patch adds a check for negative dentry.stream.valid_size to prevent this vulnerability. Co-developed-by: Seunghun Han Signed-off-by: Seunghun Han Co-developed-by: Jihoon Kwon Signed-off-by: Jihoon Kwon Signed-off-by: Jaehun Gou --- fs/exfat/namei.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c index 7eb9c67fd35f..2364b49f050a 100644 --- a/fs/exfat/namei.c +++ b/fs/exfat/namei.c @@ -642,10 +642,14 @@ static int exfat_find(struct inode *dir, const struct= qstr *qname, =20 info->type =3D exfat_get_entry_type(ep); info->attr =3D le16_to_cpu(ep->dentry.file.attr); - info->size =3D le64_to_cpu(ep2->dentry.stream.valid_size); info->valid_size =3D le64_to_cpu(ep2->dentry.stream.valid_size); info->size =3D le64_to_cpu(ep2->dentry.stream.size); =20 + if (info->valid_size < 0) { + exfat_fs_error(sb, "data valid size is invalid(%lld)", info->valid_size); + return -EIO; + } + if (unlikely(EXFAT_B_TO_CLU_ROUND_UP(info->size, sbi) > sbi->used_cluster= s)) { exfat_fs_error(sb, "data size is invalid(%lld)", info->size); return -EIO; --=20 2.43.0