- 09 Dec, 2011 1 commit
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Peter Zijlstra authored
Commit 4f2a8d3c ("printk: Fix console_sem vs logbuf_lock unlock race") introduced another silly bug where we would want to acquire an already held lock. Avoid this. Reported-by:
Andrea Arcangeli <aarcange@redhat.com> Signed-off-by:
Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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- 01 Nov, 2011 4 commits
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William Douglas authored
Currently log_prefix is testing that the first character of the log level and facility is less than '0' and greater than '9' (which is always false). Since the code being updated works because strtoul bombs out (endp isn't updated) and 0 is returned anyway just remove the check and don't change the behavior of the function. Signed-off-by:
William Douglas <william.douglas@intel.com> Signed-off-by:
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William Douglas authored
Currently log_prefix is testing that the first character of the log level and facility is less than '0' and greater than '9' (which is always false). It should be testing to see if the character less than '0' or greater than '9' instead. This patch makes that change. The code being changed worked because strtoul bombs out (endp isn't updated) and 0 is returned anyway. Signed-off-by:
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Yanmin Zhang authored
We are enabling some power features on medfield. To test suspend-2-RAM conveniently, we need turn on/off console_suspend_enabled frequently. Add a module parameter, so users could change it by: /sys/module/printk/parameters/console_suspend Signed-off-by:
Yanmin Zhang <yanmin_zhang@linux.intel.com> Signed-off-by:
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Yanmin Zhang authored
We are enabling some power features on medfield. To test suspend-2-RAM conveniently, we need turn on/off ignore_loglevel frequently without rebooting. Add a module parameter, so users can change it by: /sys/module/printk/parameters/ignore_loglevel Signed-off-by:
Yanmin Zhang <yanmin.zhang@intel.com> Signed-off-by:
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- 13 Sep, 2011 1 commit
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Thomas Gleixner authored
The logbuf_lock lock can be taken in atomic context and therefore cannot be preempted on -rt - annotate it. In mainline this change documents the low level nature of the lock - otherwise there's no functional difference. Lockdep and Sparse checking will work as usual. Signed-off-by:
Thomas Gleixner <tglx@linutronix.de> [ merged and fixed it ] Signed-off-by:
Ingo Molnar <mingo@elte.hu>
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- 25 Aug, 2011 1 commit
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Nishanth Aravamudan authored
It seems that 7bf69395 ("console: allow to retain boot console via boot option keep_bootcon") doesn't always achieve what it aims, as when printk_late_init() runs it unconditionally turns off all boot consoles. With this patch, I am able to see more messages on the boot console in KVM guests than I can without, when keep_bootcon is specified. I think it is appropriate for the relevant -stable trees. However, it's more of an annoyance than a serious bug (ideally you don't need to keep the boot console around as console handover should be working -- I was encountering a situation where the console handover wasn't working and not having the boot console available meant I couldn't see why). Signed-off-by:
Nishanth Aravamudan <nacc@us.ibm.com> Cc: David S. Miller <davem@davemloft.net> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Greg KH <gregkh@suse.de> Acked-by:
Fabio M. Di Nitto <fdinitto@redhat.com> Cc: <stable@kernel.org> [2.6.39.x, 3.0.x] Signed-off-by:
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- 10 Aug, 2011 1 commit
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Jonathan Nieder authored
syslog-ng versions before 3.3.0beta1 (2011-05-12) assume that CAP_SYS_ADMIN is sufficient to access syslog, so ever since CAP_SYSLOG was introduced (2010-11-25) they have triggered a warning. Commit ee24aebf ("cap_syslog: accept CAP_SYS_ADMIN for now") improved matters a little by making syslog-ng work again, just keeping the WARN_ONCE(). But still, this is a warning that writes a stack trace we don't care about to syslog, sets a taint flag, and alarms sysadmins when nothing worse has happened than use of an old userspace with a recent kernel. Convert the WARN_ONCE to a printk_once to avoid that while continuing to give userspace developers a hint that this is an unwanted backward-compatibility feature and won't be around forever. Reported-by:
Ralf Hildebrandt <ralf.hildebrandt@charite.de> Reported-by:
Niels <zorglub_olsen@hotmail.com> Reported-by:
Paweł Sikora <pluto@agmk.net> Signed-off-by:
Jonathan Nieder <jrnieder@gmail.com> Liked-by:
Gergely Nagy <algernon@madhouse-project.org> Acked-by:
Serge Hallyn <serge@hallyn.com> Acked-by:
James Morris <jmorris@namei.org> Signed-off-by:
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- 22 Jun, 2011 1 commit
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Peter Zijlstra authored
Fix up the fallout from commit 0b5e1c52 ("printk: Release console_sem after logbuf_lock"). The reason for unlocking the console_sem under the logbuf_lock is that a concurrent printk() might fill up the buffer but fail to acquire the console sem, resulting in a missed write to the console until a subsequent console_sem acquire/release cycle. Signed-off-by:
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- 07 Jun, 2011 1 commit
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Peter Zijlstra authored
Release console_sem after unlocking the logbuf_lock so that we don't generate wakeups while holding logbuf_lock. This avoids some lock inversion troubles once we remove the lockdep_off bits between logbuf_lock and rq->lock (prints while holding rq->lock vs doing wakeups while holding logbuf_lock). There's of course still an actual deadlock where the printk()s under rq->lock will issue a wakeup from the up() call, but lockdep won't warn about that since semaphores are not tracked. Signed-off-by:
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- 25 May, 2011 1 commit
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Mike Travis authored
On larger systems, because of the numerous ACPI, Bootmem and EFI messages, the static log buffer overflows before the larger one specified by the log_buf_len param is allocated. Minimize the overflow by allocating the new log buffer as soon as possible. On kernels without memblock, a later call to setup_log_buf from kernel/init.c is the fallback. [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: fix CONFIG_PRINTK=n build] Signed-off-by:
Mike Travis <travis@sgi.com> Cc: Yinghai Lu <yhlu.kernel@gmail.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Jack Steiner <steiner@sgi.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by:
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- 23 Mar, 2011 3 commits
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Mandeep Singh Baines authored
We've been burned by regressions/bugs which we later realized could have been triaged quicker if only we'd paid closer attention to dmesg. To make it easier to audit dmesg, we'd like to make DEFAULT_MESSAGE_LEVEL Kconfig-settable. That way we can set it to KERN_NOTICE and audit any messages <= KERN_WARNING. Signed-off-by:
Mandeep Singh Baines <msb@chromium.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Joe Perches <joe@perches.com> Cc: Olof Johansson <olofj@chromium.org> Cc: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by:
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Feng Tang authored
For a platform with many consoles like: "console=tty1 console=ttyMFD2 console=ttyS0 earlyprintk=mrst" Each time when the non "selected_console" (tty1 and ttyMFD2 here) get registered, the existing kernel message will be printed out on registered consoles again, the "mrst" early console will get some same message for 3 times, and "tty1" will get some for twice. As suggested by Andrew Morton, every time a new console is registered, it will be set as the "exclusive" console which will dump the already existing kernel messages. Signed-off-by:
Feng Tang <feng.tang@intel.com> Cc: Greg KH <gregkh@suse.de> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by:
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Fabio M. Di Nitto authored
On some architectures, the boot process involves de-registering the boot console (early boot), initialize drivers and then re-register the console. This mechanism introduces a window in which no printk can happen on the console and messages are buffered and then printed once the new console is available. If a kernel crashes during this window, all it's left on the boot console is "console [foo] enabled, bootconsole disabled" making debug of the crash rather 'interesting'. By adding "keep_bootcon" option, do not unregister the boot console, that will allow to printk everything that is happening up to the crash. The option is clearly meant only for debugging purposes as it introduces lots of duplicated info printed on console, but will make bug report from users easier as it doesn't require a kernel build just to figure out where we crash. Signed-off-by:
Fabio M. Di Nitto <fabbione@fabbione.net> Acked-by:
David S. Miller <davem@davemloft.net> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Greg KH <gregkh@suse.de> Signed-off-by:
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- 14 Mar, 2011 1 commit
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Kay Sievers authored
printk: do not mangle valid userspace syslog prefixes with /dev/kmsg Log messages passed to the kernel log by using /dev/kmsg or /dev/ttyprintk might contain a syslog prefix including the syslog facility value. This makes printk to recognize these headers properly, extract the real log level from it to use, and add the prefix as a proper prefix to the log buffer, instead of wrongly printing it as the log message text. Before: $ echo '<14>text' > /dev/kmsg $ dmesg -r <4>[135159.594810] <14>text After: $ echo '<14>text' > /dev/kmsg $ dmesg -r <14>[ 50.750654] text Cc: Lennart Poettering <lennart@poettering.net> Signed-off-by:
Kay Sievers <kay.sievers@vrfy.org> Signed-off-by:
Greg Kroah-Hartman <gregkh@suse.de>
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- 11 Feb, 2011 1 commit
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Linus Torvalds authored
In commit ce6ada35 ("security: Define CAP_SYSLOG") Serge Hallyn introduced CAP_SYSLOG, but broke backwards compatibility by no longer accepting CAP_SYS_ADMIN as an override (it would cause a warning and then reject the operation). Re-instate CAP_SYS_ADMIN - but keeping the warning - as an acceptable capability until any legacy applications have been updated. There are apparently applications out there that drop all capabilities except for CAP_SYS_ADMIN in order to access the syslog. (This is a re-implementation of a patch by Serge, cleaning the logic up and making the code more readable) Acked-by:
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- 26 Jan, 2011 1 commit
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Torben Hohn authored
The -rt patches change the console_semaphore to console_mutex. As a result, a quite large chunk of the patches changes all acquire/release_console_sem() to acquire/release_console_mutex() This commit makes things use more neutral function names which dont make implications about the underlying lock. The only real change is the return value of console_trylock which is inverted from try_acquire_console_sem() This patch also paves the way to switching console_sem from a semaphore to a mutex. [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: make console_trylock return 1 on success, per Geert] Signed-off-by:
Torben Hohn <torbenh@gmx.de> Cc: Thomas Gleixner <tglx@tglx.de> Cc: Greg KH <gregkh@suse.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Signed-off-by:
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- 13 Jan, 2011 2 commits
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Huang Ying authored
dump_list_lock is used to protect dump_list in kmsg_dumper implementation, kmsg_dump() uses it to traverse dump_list too. But if there is contention on the lock, kmsg_dump() will fail, and the valuable kernel message may be lost. This patch solves this issue with RCU. Because kmsg_dump() only read the list, no lock is needed in kmsg_dump(). So that kmsg_dump() will never fail because of lock contention. Signed-off-by:
Huang Ying <ying.huang@intel.com> Cc: "Paul E. McKenney" <paulmck@us.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
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Seiji Aguchi authored
We need to know the reason why system rebooted in support service. However, we can't inform our customers of the reason because final messages are lost on current Linux kernel. This patch improves the situation above because the final messages are saved by adding kmsg_dump() to reboot, halt, poweroff and emergency_restart path. Signed-off-by:
Seiji Aguchi <seiji.aguchi@hds.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Marco Stornelli <marco.stornelli@gmail.com> Reviewed-by:
Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Reviewed-by:
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by:
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- 17 Dec, 2010 2 commits
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Christoph Lameter authored
__get_cpu_var() can be replaced with this_cpu_read and will then use a single read instruction with implied address calculation to access the correct per cpu instance. However, the address of a per cpu variable passed to __this_cpu_read() cannot be determined (since it's an implied address conversion through segment prefixes). Therefore apply this only to uses of __get_cpu_var where the address of the variable is not used. Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Hugh Dickins <hughd@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Acked-by:
H. Peter Anvin <hpa@zytor.com> Signed-off-by:
Christoph Lameter <cl@linux.com> Signed-off-by:
Tejun Heo <tj@kernel.org>
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Kay Sievers authored
tty: add 'active' sysfs attribute to tty0 and console device Userspace can query the actual virtual console, and the configured console devices behind /dev/tt0 and /dev/console. The last entry in the list of devices is the active device, analog to the console= kernel command line option. The attribute supports poll(), which is raised when the virtual console is changed or /dev/console is reconfigured. Signed-off-by:
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- 08 Dec, 2010 2 commits
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Serge E. Hallyn authored
Eric Paris pointed out that it doesn't make sense to require both CAP_SYS_ADMIN and CAP_SYSLOG for certain syslog actions. So require CAP_SYSLOG, not CAP_SYS_ADMIN, when dmesg_restrict is set. (I'm also consolidating the now common error path) Signed-off-by:
Serge E. Hallyn <serge.hallyn@canonical.com> Acked-by:
Eric Paris <eparis@redhat.com> Acked-by:
Kees Cook <kees.cook@canonical.com> Signed-off-by:
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Eric Dumazet authored
__get_cpu_var() is a bit inefficient, lets use __this_cpu_read() and __this_cpu_write() to manipulate printk_pending. printk_needs_cpu(cpu) is called only for the current cpu : Use faster __this_cpu_read(). Remove the redundant unlikely on (cpu_is_offline(cpu)) test: # size kernel/printk.o* text data bss dec hex filename 9942 756 263488 274186 42f0a kernel/printk.o.new 9990 756 263488 274234 42f3a kernel/printk.o.old Signed-off-by:
Eric Dumazet <eric.dumazet@gmail.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Christoph Lameter <cl@linux.com> Signed-off-by:
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- 28 Nov, 2010 1 commit
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Serge E. Hallyn authored
Privileged syslog operations currently require CAP_SYS_ADMIN. Split this off into a new CAP_SYSLOG privilege which we can sanely take away from a container through the capability bounding set. With this patch, an lxc container can be prevented from messing with the host's syslog (i.e. dmesg -c). Changelog: mar 12 2010: add selinux capability2:cap_syslog perm Changelog: nov 22 2010: . port to new kernel . add a WARN_ONCE if userspace isn't using CAP_SYSLOG Signed-off-by:
Serge Hallyn <serge.hallyn@ubuntu.com> Acked-by:
Andrew G. Morgan <morgan@kernel.org> Acked-By:
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- 26 Nov, 2010 2 commits
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Heiko Carstens authored
This patch fixes a hang observed with 2.6.32 kernels where timers got enqueued on offline cpus. printk_needs_cpu() may return 1 if called on offline cpus. When a cpu gets offlined it schedules the idle process which, before killing its own cpu, will call tick_nohz_stop_sched_tick(). That function in turn will call printk_needs_cpu() in order to check if the local tick can be disabled. On offline cpus this function should naturally return 0 since regardless if the tick gets disabled or not the cpu will be dead short after. That is besides the fact that __cpu_disable() should already have made sure that no interrupts on the offlined cpu will be delivered anyway. In this case it prevents tick_nohz_stop_sched_tick() to call select_nohz_load_balancer(). No idea if that really is a problem. However what made me debug this is that on 2.6.32 the function get_nohz_load_balancer() is used within __mod_timer() to select a cpu on which a timer gets enqueued. If printk_needs_cpu() returns 1 then the nohz_load_balancer cpu doesn't get updated when a cpu gets offlined. It may contain the cpu number of an offline cpu. In turn timers get enqueued on an offline cpu and not very surprisingly they never expire and cause system hangs. This has been observed 2.6.32 kernels. On current kernels __mod_timer() uses get_nohz_timer_target() which doesn't have that problem. However there might be other problems because of the too early exit tick_nohz_stop_sched_tick() in case a cpu goes offline. Easiest way to fix this is just to test if the current cpu is offline and call printk_tick() directly which clears the condition. Alternatively I tried a cpu hotplug notifier which would clear the condition, however between calling the notifier function and printk_needs_cpu() something could have called printk() again and the problem is back again. This seems to be the safest fix. Signed-off-by:
Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by:
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Heiko Carstens authored
wake_up_klogd() may get called from preemptible context but uses __raw_get_cpu_var() to write to a per cpu variable. If it gets preempted between getting the address and writing to it, the cpu in question could be offline if the process gets scheduled back and hence writes to the per cpu data of an offline cpu. This buggy behaviour was introduced with fa33507a "printk: robustify printk, fix #2" which was supposed to fix a "using smp_processor_id() in preemptible" warning. Let's use this_cpu_write() instead which disables preemption and makes sure that the outlined scenario cannot happen. Signed-off-by:
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- 16 Nov, 2010 1 commit
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Jiri Slaby authored
Move it out of printk.c so that we can use it all over the code. There are some potential users which will be converted to that macro in next patches. Signed-off-by:
Jiri Slaby <jslaby@suse.cz> Signed-off-by:
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- 15 Nov, 2010 1 commit
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Eric Paris authored
The addition of CONFIG_SECURITY_DMESG_RESTRICT resulted in a build failure when CONFIG_PRINTK=n. This is because the capabilities code which used the new option was built even though the variable in question didn't exist. The patch here fixes this by moving the capabilities checks out of the LSM and into the caller. All (known) LSMs should have been calling the capabilities hook already so it actually makes the code organization better to eliminate the hook altogether. Signed-off-by:
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- 12 Nov, 2010 1 commit
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Dan Rosenberg authored
The kernel syslog contains debugging information that is often useful during exploitation of other vulnerabilities, such as kernel heap addresses. Rather than futilely attempt to sanitize hundreds (or thousands) of printk statements and simultaneously cripple useful debugging functionality, it is far simpler to create an option that prevents unprivileged users from reading the syslog. This patch, loosely based on grsecurity's GRKERNSEC_DMESG, creates the dmesg_restrict sysctl. When set to "0", the default, no restrictions are enforced. When set to "1", only users with CAP_SYS_ADMIN can read the kernel syslog via dmesg(8) or other mechanisms. [akpm@linux-foundation.org: explain the config option in kernel.txt] Signed-off-by:
Dan Rosenberg <drosenberg@vsecurity.com> Acked-by:
Eugene Teo <eugeneteo@kernel.org> Acked-by:
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- 26 Oct, 2010 3 commits
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Namhyung Kim authored
get_option() takes its 2nd arg as int * so passing boot_delay to it caused following warnings from sparse: kernel/printk.c:223:27: warning: incorrect type in argument 2 (different signedness) kernel/printk.c:223:27: expected int *pint kernel/printk.c:223:27: got unsigned int static [toplevel] *<noident> Since boot_delay can't grow more than 10,000 changing it to 'int *' will not produce any problem. Signed-off-by:
Namhyung Kim <namhyung@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
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Namhyung Kim authored
acquire_console_semaphore_for_printk() releases logbuf_lock but was missing proper annotation. Add it. Signed-off-by:
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Namhyung Kim authored
Move redundant 'const' after '*' to make pointer itself const Signed-off-by:
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- 12 Oct, 2010 1 commit
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Thomas Gleixner authored
It needs to be investigated whether it can be replaced by a real mutex, but that needs more thought. Signed-off-by:
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- 10 Aug, 2010 1 commit
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Andi Kleen authored
kmsg_dump takes care to sample the global variables inside a spinlock, but then goes on to use the same variables outside the spinlock region too. Use the correct variable. This will make the race window smaller. Found by gcc 4.6's new warnings. Signed-off-by:
Andi Kleen <ak@linux.intel.com> Signed-off-by:
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- 05 Aug, 2010 1 commit
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Kevin Cernekee authored
When a secondary CPU is being brought up, it is not uncommon for printk() to be invoked when cpu_online(smp_processor_id()) == 0. The case that I witnessed personally was on MIPS: http://lkml.org/lkml/2010/5/30/4 If (can_use_console() == 0), printk() will spool its output to log_buf and it will be visible in "dmesg", but that output will NOT be echoed to the console until somebody calls release_console_sem() from a CPU that is online. Therefore, the boot time messages from the new CPU can get stuck in "limbo" for a long time, and might suddenly appear on the screen when a completely unrelated event (e.g. "eth0: link is down") occurs. This patch modifies the console code so that any pending messages are automatically flushed out to the console whenever a CPU hotplug operation completes successfully or aborts. The issue was seen on 2.6.34. Original patch by Kevin Cernekee with cleanups by akpm and additional fixes by Santosh Shilimkar. This patch superseeds https://patchwork.linux-mips.org/patch/1357/ . Signed-off-by:
Kevin Cernekee <cernekee@gmail.com> To: <mingo@elte.hu> To: <akpm@linux-foundation.org> To: <simon.kagstrom@netinsight.net> To: <David.Woodhouse@intel.com> To: <lethal@linux-sh.org> Cc: <linux-kernel@vger.kernel.org> Cc: <linux-mips@linux-mips.org> Reviewed-by:
Paul Mundt <lethal@linux-sh.org> Signed-off-by:
Ralf Baechle <ralf@linux-mips.org>
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- 21 May, 2010 2 commits
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Jason Wessel authored
Certain calls from the kdb shell will call out to printk(), and any of these calls should get vectored back to the kdb_printf() so that the kdb pager and processing can be used, as well as to properly channel I/O to the polled I/O devices. CC: Randy Dunlap <rdunlap@xenotime.net> Signed-off-by:
Jason Wessel <jason.wessel@windriver.com> Acked-by:
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Jason Wessel authored
This patch contains the hooks and instrumentation into kernel which live outside the kernel/debug directory, which the kdb core will call to run commands like lsmod, dmesg, bt etc... CC: linux-arch@vger.kernel.org Signed-off-by:
Martin Hicks <mort@sgi.com>
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- 06 Mar, 2010 1 commit
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Gustavo F. Padovan authored
kernel/printk.c:72: warning: `saved_console_loglevel' defined but not used Signed-off-by:
Gustavo F. Padovan <padovan@profusion.mobi> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by:
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- 04 Feb, 2010 2 commits
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Kees Cook authored
Right now the syslog "type" action are just raw numbers which makes the source difficult to follow. This patch replaces the raw numbers with defined constants for some level of sanity. Signed-off-by:
John Johansen <john.johansen@canonical.com> Acked-by:
Serge Hallyn <serue@us.ibm.com> Signed-off-by:
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Kees Cook authored
This allows the LSM to distinguish between syslog functions originating from /proc/kmsg access and direct syscalls. By default, the commoncaps will now no longer require CAP_SYS_ADMIN to read an opened /proc/kmsg file descriptor. For example the kernel syslog reader can now drop privileges after opening /proc/kmsg, instead of staying privileged with CAP_SYS_ADMIN. MAC systems that implement security_syslog have unchanged behavior. Signed-off-by:
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