+ printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch added to -mm tree

+ printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch added to -mm tree

[akpm]

The patch titled
     Subject: printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes
has been added to the -mm tree.  Its filename is
     printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch

Before you just go and hit "reply", please:
   a) Consider who else should be cc'ed
   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
      reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/SubmitChecklist when testing your code ***

The -mm tree is included into linux-next and is updated
there every 3-4 working days

------------------------------------------------------
From: Andrew Morton <akpm@linux-foundation.org>
Subject: printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes

ERROR: else should follow close brace '}'
#160: FILE: kernel/printk/printk.c:120:
+	}
+	else

WARNING: line over 80 characters
#263: FILE: kernel/printk/printk.c:745:
+	if ((system_state != SYSTEM_BOOTING) && !(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {

total: 1 errors, 1 warnings, 250 lines checked

NOTE: For some of the reported defects, checkpatch may be able to
      mechanically convert to the typical style using --fix or --fix-inplace.

./patches/printk-add-kernel-parameter-to-control-writes-to-dev-kmsg.patch has style problems, please review.

NOTE: If any of the errors are false positives, please report
      them to the maintainer, see CHECKPATCH in MAINTAINERS.

Please run checkpatch prior to sending patches

Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/printk/printk.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff -puN kernel/printk/printk.c~printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes kernel/printk/printk.c
--- a/kernel/printk/printk.c~printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes
+++ a/kernel/printk/printk.c
@@ -117,8 +117,7 @@ static int __control_devkmsg(char *str)
 		devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
 		return 9;
 	}
-	else
-		return -EINVAL;
+	return -EINVAL;
 }
 
 static int __init control_devkmsg(char *str)
_

Patches currently in -mm which might be from akpm@linux-foundation.org are

i-need-old-gcc.patch
arch-alpha-kernel-systblss-remove-debug-check.patch
arm-arch-arm-include-asm-pageh-needs-personalityh.patch
ocfs2-improve-recovery-performance-v2-fix.patch
ocfs2-dlm-disable-bug_on-when-dlm_lock_res_dropping_ref-is-cleared-before-dlm_deref_lockres_done_handler-fix.patch
mm.patch
mm-reorganize-slab-freelist-randomization-fix.patch
mm-balloon-use-general-non-lru-movable-page-feature-fix.patch
mm-compaction-split-freepages-without-holding-the-zone-lock-fix-2.patch
mm-frontswap-convert-frontswap_enabled-to-static-key-checkpatch-fixes.patch
mm-add-nr_zsmalloc-to-vmstat-fix.patch
mm-memcg-use-consistent-gfp-flags-during-readahead-checkpatch-fixes.patch
mm-thp-make-swapin-readahead-under-down_read-of-mmap_sem-fix-2-fix.patch
mm-fix-build-warnings-in-linux-compactionh-fix.patch
mm-update-the-comment-in-__isolate_free_page-checkpatch-fixes.patch
treewide-replace-obsolete-_refok-by-__ref-checkpatch-fixes.patch
printk-create-pr_level-functions-fix.patch
printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch
kexec-ensure-user-memory-sizes-do-not-wrap-fix.patch
kexec-allow-architectures-to-override-boot-mapping-fix.patch
allow-kdump-with-crash_kexec_post_notifiers-fix.patch
linux-next-rejects.patch
drivers-net-wireless-intel-iwlwifi-dvm-calibc-fix-min-warning.patch
bitmap-bitmap_equal-memcmp-optimization-fix.patch
kernel-forkc-export-kernel_thread-to-modules.patch
slab-leaks3-default-y.patch

Re: + printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch added to -mm tree

[Borislav Petkov]

Hi Andrew,

On Mon, Jul 18, 2016 at 02:27:48PM -0700, akpm@linux-foundation.org wrote:
> 
> The patch titled
>      Subject: printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes
> has been added to the -mm tree.  Its filename is
>      printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch
> 
> This patch should soon appear at
>     http://ozlabs.org/~akpm/mmots/broken-out/printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch
> and later at
>     http://ozlabs.org/~akpm/mmotm/broken-out/printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes.patch
> 
> Before you just go and hit "reply", please:
>    a) Consider who else should be cc'ed
>    b) Prefer to cc a suitable mailing list as well
>    c) Ideally: find the original patch on the mailing list and do a
>       reply-to-all to that, adding suitable additional cc's
> 
> *** Remember to use Documentation/SubmitChecklist when testing your code ***
> 
> The -mm tree is included into linux-next and is updated
> there every 3-4 working days
> 
> ------------------------------------------------------
> From: Andrew Morton <akpm@linux-foundation.org>
> Subject: printk-add-kernel-parameter-to-control-writes-to-dev-kmsg-checkpatch-fixes
> 
> ERROR: else should follow close brace '}'
> #160: FILE: kernel/printk/printk.c:120:
> +	}
> +	else

Thanks for catching this, here's an updated 2/2 patch with the above
integrated and the SYSTEM_BOOTING check removed because we set
system_state to SYSTEM_RUNNING before we start init.

---
From: Borislav Petkov <bp@suse.de>
Date: Tue, 14 Jun 2016 11:55:58 +0200
Subject: [PATCH -v5.1] printk: Add kernel parameter to control writes to /dev/kmsg
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Add a "printk.devkmsg" kernel command line parameter which controls how
userspace writes into /dev/kmsg. It has three options:

* ratelimit - ratelimit logging from userspace.
* on  - unlimited logging from userspace
* off - logging from userspace gets ignored

The default setting is to ratelimit the messages written to it.

This changes the kernel default setting of "on" to "ratelimit" and we
do that because we want to keep userspace spamming /dev/kmsg to sane
levels. This is especially moot when a small kernel log buffer wraps
around and messages get lost. So the ratelimiting setting should be a
sane setting where kernel messages should have a bit higher chance of
survival from all the spamming.

Furthermore, we can control the logging from a lower priority sysctl
interface - kernel.printk_devkmsg.

That interface will succeed only if printk.devkmsg *hasn't* been
supplied on the command line. If it has, then printk.devkmsg is a
one-time setting which remains for the duration of the system lifetime.
This "locking" of the setting is to prevent userspace from changing the
logging on us through sysctl(2).

This patch is based on previous patches from Linus and Steven.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Young <dyoung@redhat.com>
Cc: Franck Bui <fbui@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
 Documentation/kernel-parameters.txt |   7 ++
 Documentation/sysctl/kernel.txt     |  14 ++++
 include/linux/printk.h              |   9 +++
 kernel/printk/printk.c              | 142 ++++++++++++++++++++++++++++++++++--
 kernel/sysctl.c                     |   7 ++
 5 files changed, 171 insertions(+), 8 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 82b42c958d1c..a8e9f0bd7801 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3150,6 +3150,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
 			default: disabled
 
+	printk.devkmsg={on,off,ratelimit}
+			Control writing to /dev/kmsg.
+			on - unlimited logging to /dev/kmsg from userspace
+			off - logging to /dev/kmsg disabled
+			ratelimit - ratelimit the logging
+			Default: ratelimit
+
 	printk.time=	Show timing data prefixed to each printk message line
 			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
 
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index a3683ce2a2f3..378421d423fa 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -752,6 +752,20 @@ send before ratelimiting kicks in.
 
 ==============================================================
 
+printk_devkmsg:
+
+Control the logging to /dev/kmsg from userspace:
+
+ratelimit: default, ratelimited
+on: unlimited logging to /dev/kmsg from userspace
+off: logging to /dev/kmsg disabled
+
+The kernel command line parameter printk.devkmsg= overrides this and is
+a one-time setting until next reboot: once set, it cannot be changed by
+this sysctl interface anymore.
+
+==============================================================
+
 randomize_va_space:
 
 This option can be used to select the type of process address
diff --git a/include/linux/printk.h b/include/linux/printk.h
index f4da695fd615..9c21535e5714 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -61,6 +61,11 @@ static inline void console_verbose(void)
 		console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
 }
 
+/* strlen("ratelimit") + 1 */
+#define DEVKMSG_STR_MAX_SIZE 10
+extern char devkmsg_log_str[];
+struct ctl_table;
+
 struct va_format {
 	const char *fmt;
 	va_list *va;
@@ -172,6 +177,10 @@ extern int printk_delay_msec;
 extern int dmesg_restrict;
 extern int kptr_restrict;
 
+extern int
+devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, void __user *buf,
+			  size_t *lenp, loff_t *ppos);
+
 extern void wake_up_klogd(void);
 
 char *log_buf_addr_get(void);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 60cdf6386763..d62d4ace64ab 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -86,6 +86,111 @@ static struct lockdep_map console_lock_dep_map = {
 };
 #endif
 
+enum devkmsg_log_bits {
+	__DEVKMSG_LOG_BIT_ON = 0,
+	__DEVKMSG_LOG_BIT_OFF,
+	__DEVKMSG_LOG_BIT_LOCK,
+};
+
+enum devkmsg_log_masks {
+	DEVKMSG_LOG_MASK_ON             = BIT(__DEVKMSG_LOG_BIT_ON),
+	DEVKMSG_LOG_MASK_OFF            = BIT(__DEVKMSG_LOG_BIT_OFF),
+	DEVKMSG_LOG_MASK_LOCK           = BIT(__DEVKMSG_LOG_BIT_LOCK),
+};
+
+/* Keep both the 'on' and 'off' bits clear, i.e. ratelimit by default: */
+#define DEVKMSG_LOG_MASK_DEFAULT	0
+
+static unsigned int __read_mostly devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
+
+static int __control_devkmsg(char *str)
+{
+	if (!str)
+		return -EINVAL;
+
+	if (!strncmp(str, "on", 2)) {
+		devkmsg_log = DEVKMSG_LOG_MASK_ON;
+		return 2;
+	} else if (!strncmp(str, "off", 3)) {
+		devkmsg_log = DEVKMSG_LOG_MASK_OFF;
+		return 3;
+	} else if (!strncmp(str, "ratelimit", 9)) {
+		devkmsg_log = DEVKMSG_LOG_MASK_DEFAULT;
+		return 9;
+	}
+	return -EINVAL;
+}
+
+static int __init control_devkmsg(char *str)
+{
+	if (__control_devkmsg(str) < 0)
+		return 1;
+
+	/*
+	 * Set sysctl string accordingly:
+	 */
+	if (devkmsg_log == DEVKMSG_LOG_MASK_ON) {
+		memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
+		strncpy(devkmsg_log_str, "on", 2);
+	} else if (devkmsg_log == DEVKMSG_LOG_MASK_OFF) {
+		memset(devkmsg_log_str, 0, DEVKMSG_STR_MAX_SIZE);
+		strncpy(devkmsg_log_str, "off", 3);
+	}
+	/* else "ratelimit" which is set by default. */
+
+	/*
+	 * Sysctl cannot change it anymore. The kernel command line setting of
+	 * this parameter is to force the setting to be permanent throughout the
+	 * runtime of the system. This is a precation measure against userspace
+	 * trying to be a smarta** and attempting to change it up on us.
+	 */
+	devkmsg_log |= DEVKMSG_LOG_MASK_LOCK;
+
+	return 0;
+}
+__setup("printk.devkmsg=", control_devkmsg);
+
+char devkmsg_log_str[DEVKMSG_STR_MAX_SIZE] = "ratelimit";
+
+int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
+			      void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	char old_str[DEVKMSG_STR_MAX_SIZE];
+	unsigned int old;
+	int err;
+
+	if (write) {
+		if (devkmsg_log & DEVKMSG_LOG_MASK_LOCK)
+			return -EINVAL;
+
+		old = devkmsg_log;
+		strncpy(old_str, devkmsg_log_str, DEVKMSG_STR_MAX_SIZE);
+	}
+
+	err = proc_dostring(table, write, buffer, lenp, ppos);
+	if (err)
+		return err;
+
+	if (write) {
+		err = __control_devkmsg(devkmsg_log_str);
+
+		/*
+		 * Do not accept an unknown string OR a known string with
+		 * trailing crap...
+		 */
+		if (err < 0 || (err + 1 != *lenp)) {
+
+			/* ... and restore old setting. */
+			devkmsg_log = old;
+			strncpy(devkmsg_log_str, old_str, DEVKMSG_STR_MAX_SIZE);
+
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
 /*
  * Number of registered extended console drivers.
  *
@@ -614,6 +719,7 @@ struct devkmsg_user {
 	u64 seq;
 	u32 idx;
 	enum log_flags prev;
+	struct ratelimit_state rs;
 	struct mutex lock;
 	char buf[CONSOLE_EXT_LOG_MAX];
 };
@@ -623,11 +729,24 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from)
 	char *buf, *line;
 	int level = default_message_loglevel;
 	int facility = 1;	/* LOG_USER */
+	struct file *file = iocb->ki_filp;
+	struct devkmsg_user *user = file->private_data;
 	size_t len = iov_iter_count(from);
 	ssize_t ret = len;
 
-	if (len > LOG_LINE_MAX)
+	if (!user || len > LOG_LINE_MAX)
 		return -EINVAL;
+
+	/* Ignore when user logging is disabled. */
+	if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
+		return len;
+
+	/* Ratelimit when not explicitly enabled. */
+	if (!(devkmsg_log & DEVKMSG_LOG_MASK_ON)) {
+		if (!___ratelimit(&user->rs, current->comm))
+			return ret;
+	}
+
 	buf = kmalloc(len+1, GFP_KERNEL);
 	if (buf == NULL)
 		return -ENOMEM;
@@ -800,19 +919,24 @@ static int devkmsg_open(struct inode *inode, struct file *file)
 	struct devkmsg_user *user;
 	int err;
 
-	/* write-only does not need any file context */
-	if ((file->f_flags & O_ACCMODE) == O_WRONLY)
-		return 0;
+	if (devkmsg_log & DEVKMSG_LOG_MASK_OFF)
+		return -EPERM;
 
-	err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
-				       SYSLOG_FROM_READER);
-	if (err)
-		return err;
+	/* write-only does not need any file context */
+	if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
+		err = check_syslog_permissions(SYSLOG_ACTION_READ_ALL,
+					       SYSLOG_FROM_READER);
+		if (err)
+			return err;
+	}
 
 	user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
 	if (!user)
 		return -ENOMEM;
 
+	ratelimit_default_init(&user->rs);
+	ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
+
 	mutex_init(&user->lock);
 
 	raw_spin_lock_irq(&logbuf_lock);
@@ -831,6 +955,8 @@ static int devkmsg_release(struct inode *inode, struct file *file)
 	if (!user)
 		return 0;
 
+	ratelimit_state_exit(&user->rs);
+
 	mutex_destroy(&user->lock);
 	kfree(user);
 	return 0;
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 87b2fc38398b..0d9fe53682bb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -814,6 +814,13 @@ static struct ctl_table kern_table[] = {
 		.extra2		= &ten_thousand,
 	},
 	{
+		.procname	= "printk_devkmsg",
+		.data		= devkmsg_log_str,
+		.maxlen		= DEVKMSG_STR_MAX_SIZE,
+		.mode		= 0644,
+		.proc_handler	= devkmsg_sysctl_set_loglvl,
+	},
+	{
 		.procname	= "dmesg_restrict",
 		.data		= &dmesg_restrict,
 		.maxlen		= sizeof(int),
-- 
2.8.4

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--

Re: [PATCH -v5.1] printk: Add kernel parameter to control writes to /dev/kmsg

[kbuild test robot]

[-- Attachment #1: Type: text/plain, Size: 2798 bytes --]

Hi,

[auto build test ERROR on stable/master]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Borislav-Petkov/printk-Add-kernel-parameter-to-control-writes-to-dev-kmsg/20160725-003035
base:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git master
config: x86_64-randconfig-x012-201630 (attached as .config)
compiler: gcc-6 (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   kernel/printk/printk.c: In function 'devkmsg_open':
>> kernel/printk/printk.c:937:2: error: implicit declaration of function 'ratelimit_default_init' [-Werror=implicit-function-declaration]
     ratelimit_default_init(&user->rs);
     ^~~~~~~~~~~~~~~~~~~~~~
>> kernel/printk/printk.c:938:2: error: implicit declaration of function 'ratelimit_set_flags' [-Werror=implicit-function-declaration]
     ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
     ^~~~~~~~~~~~~~~~~~~
>> kernel/printk/printk.c:938:33: error: 'RATELIMIT_MSG_ON_RELEASE' undeclared (first use in this function)
     ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
                                    ^~~~~~~~~~~~~~~~~~~~~~~~
   kernel/printk/printk.c:938:33: note: each undeclared identifier is reported only once for each function it appears in
   kernel/printk/printk.c: In function 'devkmsg_release':
>> kernel/printk/printk.c:958:2: error: implicit declaration of function 'ratelimit_state_exit' [-Werror=implicit-function-declaration]
     ratelimit_state_exit(&user->rs);
     ^~~~~~~~~~~~~~~~~~~~
   cc1: some warnings being treated as errors

vim +/ratelimit_default_init +937 kernel/printk/printk.c

   931		}
   932	
   933		user = kmalloc(sizeof(struct devkmsg_user), GFP_KERNEL);
   934		if (!user)
   935			return -ENOMEM;
   936	
 > 937		ratelimit_default_init(&user->rs);
 > 938		ratelimit_set_flags(&user->rs, RATELIMIT_MSG_ON_RELEASE);
   939	
   940		mutex_init(&user->lock);
   941	
   942		raw_spin_lock_irq(&logbuf_lock);
   943		user->idx = log_first_idx;
   944		user->seq = log_first_seq;
   945		raw_spin_unlock_irq(&logbuf_lock);
   946	
   947		file->private_data = user;
   948		return 0;
   949	}
   950	
   951	static int devkmsg_release(struct inode *inode, struct file *file)
   952	{
   953		struct devkmsg_user *user = file->private_data;
   954	
   955		if (!user)
   956			return 0;
   957	
 > 958		ratelimit_state_exit(&user->rs);
   959	
   960		mutex_destroy(&user->lock);
   961		kfree(user);

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 18881 bytes --]

Re: [PATCH -v5.1] printk: Add kernel parameter to control writes to /dev/kmsg

[Borislav Petkov]

On Mon, Jul 25, 2016 at 12:55:55AM +0800, kbuild test robot wrote:
> Hi,
> 
> [auto build test ERROR on stable/master]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
> 
> url:    https://github.com/0day-ci/linux/commits/Borislav-Petkov/printk-Add-kernel-parameter-to-control-writes-to-dev-kmsg/20160725-003035
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git master

Yes, that's definitely the wrong tree.

Those patches are queued in the mm tree, you can test that one.

Thanks.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--