From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2AACB3BCD05; Thu, 16 Jul 2026 14:08:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210891; cv=none; b=DF1Dx/QBmu38sViLEBvM2T3X7aTzEGmDfHPqYNrdlsr6nVprwG0K74eTrZhGEr8Fa9OkCvch5b/7+p5WEfAwndTRNTglAUL3CEeRIdFHduNxzWInGNFYF1NLB2iYlDN7QRdE9MtuSZwkdENvjL/WYw2LBmSN/wFhX57+KV6nEHo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784210891; c=relaxed/simple; bh=vR0fDXJ7blYWW0UvpMVC6MM0te0Y/HawaROzvbyWfyA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=byOEEr8WvBcw7G1e++YlAHAcd849qUdcdi4G7Nzk9Swu+mLt6iq3CpSBqksyFK7rME2aDnpK2OuZfyYDGhfTEr9HuhAvDH1kqWrGzWs0kaXbYVmffAGhc2uyeB2mrDj2FkUDfa5w0xZWW7u8x6BSsu29A00wvzYQZFM7DzY5//k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nj/DVLVL; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="nj/DVLVL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5D1401F000E9; Thu, 16 Jul 2026 14:08:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784210888; bh=pxU4ccuFyfaqoKOJYT/67dYEypz7J2Sp6r/jPWdao04=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nj/DVLVL5/IBMX1TVLOXqgzAWd8P3COgS8rLbgFdCA5yMtr/85IMR0haC2BeOmZA+ BItVnJdggYQe5AkzjFA077q7axPUf4tcEBrWs+NLlatUzDmZ85GLzmZPonti6Lcp70 sYrw21fAKNPHEtIel3hb0Dj01Qr7rpjDwyH6mvb0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gil Portnoy , Namjae Jeon , Steve French Subject: [PATCH 6.18 218/480] ksmbd: add a permission check for FSCTL_SET_ZERO_DATA Date: Thu, 16 Jul 2026 15:29:25 +0200 Message-ID: <20260716133049.448289900@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260716133044.672218725@linuxfoundation.org> References: <20260716133044.672218725@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gil Portnoy commit 3320ba068198adc144c89d6661b805acce01735b upstream. FSCTL_SET_ZERO_DATA in smb2_ioctl() destroys file data via ksmbd_vfs_zero_data() -> vfs_fallocate(PUNCH_HOLE/ZERO_RANGE) after checking only the share-level KSMBD_TREE_CONN_FLAG_WRITABLE, with no per-handle access check. A handle opened with only FILE_WRITE_ATTRIBUTES still yields an FMODE_WRITE filp (FILE_WRITE_ATTRIBUTES is part of FILE_WRITE_DESIRE_ACCESS_LE, so smb2_create_open_flags() opens it O_WRONLY), so the vfs_fallocate FMODE_WRITE check does not stop it; only the missing fp->daccess gate would. Reproduced on mainline 7.1-rc7 with KASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle zeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to (6/6; a FILE_READ_DATA-only handle was correctly denied). This is the unfixed sibling of commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE"). Because SET_ZERO_DATA writes data (not an attribute), require FILE_WRITE_DATA. Cc: stable@vger.kernel.org Signed-off-by: Gil Portnoy Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Greg Kroah-Hartman --- fs/smb/server/smb2pdu.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/fs/smb/server/smb2pdu.c +++ b/fs/smb/server/smb2pdu.c @@ -8488,6 +8488,12 @@ int smb2_ioctl(struct ksmbd_work *work) goto out; } + if (!(fp->daccess & FILE_WRITE_DATA_LE)) { + ksmbd_fd_put(work, fp); + ret = -EACCES; + goto out; + } + ret = ksmbd_vfs_zero_data(work, fp, off, len); ksmbd_fd_put(work, fp); if (ret < 0)