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Thu, 16 Apr 2020 06:02:43 +0000 Received: from b03ledav001.gho.boulder.ibm.com (b03ledav001.gho.boulder.ibm.com [9.17.130.232]) by b03cxnp08026.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 03G62g7Y58720548 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Apr 2020 06:02:42 GMT Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EFCBD6E052; Thu, 16 Apr 2020 06:02:41 +0000 (GMT) Received: from b03ledav001.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 31CA46E04C; Thu, 16 Apr 2020 06:02:41 +0000 (GMT) Received: from [9.70.82.143] (unknown [9.70.82.143]) by b03ledav001.gho.boulder.ibm.com (Postfix) with ESMTP; Thu, 16 Apr 2020 06:02:41 +0000 (GMT) Subject: [PATCH v11 06/14] powerpc/vas: Take reference to PID and mm for user space windows From: Haren Myneni To: mpe@ellerman.id.au In-Reply-To: <1587016214.2275.1036.camel@hbabu-laptop> References: <1587016214.2275.1036.camel@hbabu-laptop> Content-Type: text/plain; charset="UTF-8" Date: Wed, 15 Apr 2020 23:02:16 -0700 Message-ID: <1587016936.2275.1057.camel@hbabu-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.676 definitions=2020-04-16_01:2020-04-14, 2020-04-16 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 adultscore=0 spamscore=0 phishscore=0 mlxscore=0 suspectscore=3 priorityscore=1501 bulkscore=0 mlxlogscore=999 lowpriorityscore=0 clxscore=1015 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004160033 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mikey@neuling.org, srikar@linux.vnet.ibm.com, frederic.barrat@fr.ibm.com, ajd@linux.ibm.com, linux-kernel@vger.kernel.org, npiggin@gmail.com, hch@infradead.org, oohall@gmail.com, clg@kaod.org, sukadev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, herbert@gondor.apana.org.au Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" When process opens a window, its pid and tgid will be saved in the vas_window struct. This window will be closed when the process exits. The kernel handles NX faults by updating CSB or send SEGV signal to pid of the process if the userspace csb addr is invalid. In multi-thread applications, a window can be opened by a child thread, but it will not be closed when this thread exits. It is expected that the parent will clean up all resources including NX windows opened by child threads. A child thread can send NX requests using this window and could be killed before completion is reported. If the pid assigned to this thread is reused while requests are pending, a failure SEGV would be directed to the wrong place. To prevent reusing the pid, take references to pid and mm when the window is opened and release them when when the window is closed. Then if child thread is not running, SEGV signal will be sent to thread group leader (tgid). Signed-off-by: Haren Myneni --- arch/powerpc/platforms/powernv/vas-debug.c | 2 +- arch/powerpc/platforms/powernv/vas-window.c | 50 ++++++++++++++++++++++++++--- arch/powerpc/platforms/powernv/vas.h | 9 +++++- 3 files changed, 55 insertions(+), 6 deletions(-) diff --git a/arch/powerpc/platforms/powernv/vas-debug.c b/arch/powerpc/platforms/powernv/vas-debug.c index 09e63df..ef9a717 100644 --- a/arch/powerpc/platforms/powernv/vas-debug.c +++ b/arch/powerpc/platforms/powernv/vas-debug.c @@ -38,7 +38,7 @@ static int info_show(struct seq_file *s, void *private) seq_printf(s, "Type: %s, %s\n", cop_to_str(window->cop), window->tx_win ? "Send" : "Receive"); - seq_printf(s, "Pid : %d\n", window->pid); + seq_printf(s, "Pid : %d\n", vas_window_pid(window)); unlock: mutex_unlock(&vas_mutex); diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c index dc46bf6..063cda2 100644 --- a/arch/powerpc/platforms/powernv/vas-window.c +++ b/arch/powerpc/platforms/powernv/vas-window.c @@ -12,6 +12,8 @@ #include #include #include +#include +#include #include #include #include "vas.h" @@ -876,8 +878,6 @@ struct vas_window *vas_rx_win_open(int vasid, enum vas_cop_type cop, rxwin->user_win = rxattr->user_win; rxwin->cop = cop; rxwin->wcreds_max = rxattr->wcreds_max ?: VAS_WCREDS_DEFAULT; - if (rxattr->user_win) - rxwin->pid = task_pid_vnr(current); init_winctx_for_rxwin(rxwin, rxattr, &winctx); init_winctx_regs(rxwin, &winctx); @@ -1027,7 +1027,6 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop, txwin->tx_win = 1; txwin->rxwin = rxwin; txwin->nx_win = txwin->rxwin->nx_win; - txwin->pid = attr->pid; txwin->user_win = attr->user_win; txwin->wcreds_max = attr->wcreds_max ?: VAS_WCREDS_DEFAULT; @@ -1057,6 +1056,40 @@ struct vas_window *vas_tx_win_open(int vasid, enum vas_cop_type cop, rc = set_thread_uses_vas(); if (rc) goto free_window; + + /* + * Window opened by a child thread may not be closed when + * it exits. So take reference to its pid and release it + * when the window is free by parent thread. + * Acquire a reference to the task's pid to make sure + * pid will not be re-used - needed only for multithread + * applications. + */ + txwin->pid = get_task_pid(current, PIDTYPE_PID); + /* + * Acquire a reference to the task's mm. + */ + txwin->mm = get_task_mm(current); + + if (!txwin->mm) { + put_pid(txwin->pid); + pr_err("VAS: pid(%d): mm_struct is not found\n", + current->pid); + rc = -EPERM; + goto free_window; + } + + mmgrab(txwin->mm); + mmput(txwin->mm); + mm_context_add_copro(txwin->mm); + /* + * Process closes window during exit. In the case of + * multithread application, the child thread can open + * window and can exit without closing it. Expects parent + * thread to use and close the window. So do not need + * to take pid reference for parent thread. + */ + txwin->tgid = find_get_pid(task_tgid_vnr(current)); } set_vinst_win(vinst, txwin); @@ -1257,8 +1290,17 @@ int vas_win_close(struct vas_window *window) poll_window_castout(window); /* if send window, drop reference to matching receive window */ - if (window->tx_win) + if (window->tx_win) { + if (window->user_win) { + /* Drop references to pid and mm */ + put_pid(window->pid); + if (window->mm) { + mm_context_remove_copro(window->mm); + mmdrop(window->mm); + } + } put_rx_win(window->rxwin); + } vas_window_free(window); diff --git a/arch/powerpc/platforms/powernv/vas.h b/arch/powerpc/platforms/powernv/vas.h index 88d084d..2a04072 100644 --- a/arch/powerpc/platforms/powernv/vas.h +++ b/arch/powerpc/platforms/powernv/vas.h @@ -355,7 +355,9 @@ struct vas_window { bool user_win; /* True if user space window */ void *hvwc_map; /* HV window context */ void *uwc_map; /* OS/User window context */ - pid_t pid; /* Linux process id of owner */ + struct pid *pid; /* Linux process id of owner */ + struct pid *tgid; /* Thread group ID of owner */ + struct mm_struct *mm; /* Linux process mm_struct */ int wcreds_max; /* Window credits */ char *dbgname; @@ -430,6 +432,11 @@ struct vas_winctx { extern void vas_window_free_dbgdir(struct vas_window *win); extern int vas_setup_fault_window(struct vas_instance *vinst); +static inline int vas_window_pid(struct vas_window *window) +{ + return pid_vnr(window->pid); +} + static inline void vas_log_write(struct vas_window *win, char *name, void *regptr, u64 val) { -- 1.8.3.1