From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.codeaurora.org by pdx-caf-mail.web.codeaurora.org (Dovecot) with LMTP id pdEJLN5HGVs9QQAAmS7hNA ; Thu, 07 Jun 2018 14:59:40 +0000 Received: by smtp.codeaurora.org (Postfix, from userid 1000) id 246AF608BF; Thu, 7 Jun 2018 14:59:40 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by smtp.codeaurora.org (Postfix) with ESMTP id 3EE0F601C3; Thu, 7 Jun 2018 14:59:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 3EE0F601C3 Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=decadent.org.uk Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935719AbeFGO7g (ORCPT + 25 others); Thu, 7 Jun 2018 10:59:36 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41291 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935702AbeFGO7e (ORCPT ); Thu, 7 Jun 2018 10:59:34 -0400 Received: from [148.252.241.226] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1fQvbg-0005Zi-Gp; Thu, 07 Jun 2018 15:09:40 +0100 Received: from ben by deadeye with local (Exim 4.91) (envelope-from ) id 1fQvb6-00030b-Ba; Thu, 07 Jun 2018 15:09:04 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Linus Torvalds" , "Josh Poimboeuf" , "Michael Kerrisk" , "Randy Dunlap" , "Al Viro" , "Joe Lawrence" , "Mikulas Patocka" , "Jens Axboe" Date: Thu, 07 Jun 2018 15:05:21 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 208/410] pipe: add proc_dopipe_max_size() to safely assign pipe_max_size In-Reply-To: X-SA-Exim-Connect-IP: 148.252.241.226 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.57-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Joe Lawrence commit 7a8d181949fb2c16be00f8cdb354794a30e46b39 upstream. pipe_max_size is assigned directly via procfs sysctl: static struct ctl_table fs_table[] = { ... { .procname = "pipe-max-size", .data = &pipe_max_size, .maxlen = sizeof(int), .mode = 0644, .proc_handler = &pipe_proc_fn, .extra1 = &pipe_min_size, }, ... int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf, size_t *lenp, loff_t *ppos) { ... ret = proc_dointvec_minmax(table, write, buf, lenp, ppos) ... and then later rounded in-place a few statements later: ... pipe_max_size = round_pipe_size(pipe_max_size); ... This leaves a window of time between initial assignment and rounding that may be visible to other threads. (For example, one thread sets a non-rounded value to pipe_max_size while another reads its value.) Similar reads of pipe_max_size are potentially racy: pipe.c :: alloc_pipe_info() pipe.c :: pipe_set_size() Add a new proc_dopipe_max_size() that consolidates reading the new value from the user buffer, verifying bounds, and calling round_pipe_size() with a single assignment to pipe_max_size. Link: http://lkml.kernel.org/r/1507658689-11669-4-git-send-email-joe.lawrence@redhat.com Signed-off-by: Joe Lawrence Reported-by: Mikulas Patocka Reviewed-by: Mikulas Patocka Cc: Al Viro Cc: Jens Axboe Cc: Michael Kerrisk Cc: Randy Dunlap Cc: Josh Poimboeuf Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [bwh: Backported to 3.16: Continue using int sysctl functions because we don't have proper unsigned int support] Signed-off-by: Ben Hutchings --- --- a/fs/pipe.c +++ b/fs/pipe.c @@ -1008,7 +1008,7 @@ const struct file_operations pipefifo_fo * Currently we rely on the pipe array holding a power-of-2 number * of pages. Returns 0 on error. */ -static inline unsigned int round_pipe_size(unsigned int size) +unsigned int round_pipe_size(unsigned int size) { unsigned long nr_pages; @@ -1112,25 +1112,13 @@ out_revert_acct: } /* - * This should work even if CONFIG_PROC_FS isn't set, as proc_dointvec_minmax + * This should work even if CONFIG_PROC_FS isn't set, as proc_dopipe_max_size * will return an error. */ int pipe_proc_fn(struct ctl_table *table, int write, void __user *buf, size_t *lenp, loff_t *ppos) { - unsigned int rounded_pipe_max_size; - int ret; - - ret = proc_dointvec_minmax(table, write, buf, lenp, ppos); - if (ret < 0 || !write) - return ret; - - rounded_pipe_max_size = round_pipe_size(pipe_max_size); - if (rounded_pipe_max_size == 0) - return -EINVAL; - - pipe_max_size = rounded_pipe_max_size; - return ret; + return proc_dopipe_max_size(table, write, buf, lenp, ppos); } /* --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -149,5 +149,6 @@ long pipe_fcntl(struct file *, unsigned struct pipe_inode_info *get_pipe_info(struct file *file); int create_pipe_files(struct file **, int); +unsigned int round_pipe_size(unsigned int size); #endif --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -45,6 +45,9 @@ extern int proc_dointvec(struct ctl_tabl void __user *, size_t *, loff_t *); extern int proc_dointvec_minmax(struct ctl_table *, int, void __user *, size_t *, loff_t *); +extern int proc_dopipe_max_size(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos); extern int proc_dointvec_jiffies(struct ctl_table *, int, void __user *, size_t *, loff_t *); extern int proc_dointvec_userhz_jiffies(struct ctl_table *, int, --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -64,6 +64,7 @@ #include #include #include +#include #include #include @@ -2222,6 +2223,47 @@ int proc_dointvec_minmax(struct ctl_tabl do_proc_dointvec_minmax_conv, ¶m); } +struct do_proc_dopipe_max_size_conv_param { + unsigned int *min; +}; + +static int do_proc_dopipe_max_size_conv(bool *negp, unsigned long *lvalp, + int *valp, int write, void *data) +{ + struct do_proc_dopipe_max_size_conv_param *param = data; + + if (write) { + unsigned int val = round_pipe_size(*lvalp); + + if (*negp || val == 0) + return -EINVAL; + + if (param->min && *param->min > val) + return -ERANGE; + + if (*lvalp > UINT_MAX) + return -EINVAL; + + *valp = val; + } else { + unsigned int val = *valp; + *negp = false; + *lvalp = (unsigned long) val; + } + + return 0; +} + +int proc_dopipe_max_size(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + struct do_proc_dopipe_max_size_conv_param param = { + .min = (unsigned int *) table->extra1, + }; + return do_proc_dointvec(table, write, buffer, lenp, ppos, + do_proc_dopipe_max_size_conv, ¶m); +} + static void validate_coredump_safety(void) { #ifdef CONFIG_COREDUMP @@ -2737,6 +2779,12 @@ int proc_dointvec_minmax(struct ctl_tabl return -ENOSYS; } +int proc_dopipe_max_size(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + return -ENOSYS; +} + int proc_dointvec_jiffies(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { @@ -2778,6 +2826,7 @@ int proc_doulongvec_ms_jiffies_minmax(st EXPORT_SYMBOL(proc_dointvec); EXPORT_SYMBOL(proc_dointvec_jiffies); EXPORT_SYMBOL(proc_dointvec_minmax); +EXPORT_SYMBOL_GPL(proc_dopipe_max_size); EXPORT_SYMBOL(proc_dointvec_userhz_jiffies); EXPORT_SYMBOL(proc_dointvec_ms_jiffies); EXPORT_SYMBOL(proc_dostring);