1. 08 Aug, 2014 1 commit
  2. 23 Jun, 2014 1 commit
    • Aaron Tomlin's avatar
      kernel/watchdog.c: print traces for all cpus on lockup detection · ed235875
      Aaron Tomlin authored
      A 'softlockup' is defined as a bug that causes the kernel to loop in
      kernel mode for more than a predefined period to time, without giving
      other tasks a chance to run.
      Currently, upon detection of this condition by the per-cpu watchdog
      task, debug information (including a stack trace) is sent to the system
      On some occasions, we have observed that the "victim" rather than the
      actual "culprit" (i.e.  the owner/holder of the contended resource) is
      reported to the user.  Often this information has proven to be
      insufficient to assist debugging efforts.
      To avoid loss of useful debug information, for architectures which
      support NMI, this patch makes it possible to improve soft lockup
      reporting.  This is accomplished by issuing an NMI to each cpu to obtain
      a stack trace.
      If NMI is not supported we just revert back to the old method.  A sysctl
      and boot-time parameter is available to toggle this feature.
      [dzickus@redhat.com: add CONFIG_SMP in certain areas]
      [akpm@linux-foundation.org: additional CONFIG_SMP=n optimisations]
      [mq@suse.cz: fix warning]
      Signed-off-by: default avatarAaron Tomlin <atomlin@redhat.com>
      Signed-off-by: default avatarDon Zickus <dzickus@redhat.com>
      Cc: David S. Miller <davem@davemloft.net>
      Cc: Mateusz Guzik <mguzik@redhat.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Signed-off-by: default avatarJan Moskyto Matejka <mq@suse.cz>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  3. 06 Jun, 2014 1 commit
    • Kees Cook's avatar
      sysctl: allow for strict write position handling · f4aacea2
      Kees Cook authored
      When writing to a sysctl string, each write, regardless of VFS position,
      begins writing the string from the start.  This means the contents of
      the last write to the sysctl controls the string contents instead of the
        open("/proc/sys/kernel/modprobe", O_WRONLY)   = 1
        write(1, "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"..., 4096) = 4096
        write(1, "/bin/true", 9)                = 9
        close(1)                                = 0
        $ cat /proc/sys/kernel/modprobe
      Expected behaviour would be to have the sysctl be "AAAA..." capped at
      maxlen (in this case KMOD_PATH_LEN: 256), instead of truncating to the
      contents of the second write.  Similarly, multiple short writes would
      not append to the sysctl.
      The old behavior is unlike regular POSIX files enough that doing audits
      of software that interact with sysctls can end up in unexpected or
      dangerous situations.  For example, "as long as the input starts with a
      trusted path" turns out to be an insufficient filter, as what must also
      happen is for the input to be entirely contained in a single write
      syscall -- not a common consideration, especially for high level tools.
      This provides kernel.sysctl_writes_strict as a way to make this behavior
      act in a less surprising manner for strings, and disallows non-zero file
      position when writing numeric sysctls (similar to what is already done
      when reading from non-zero file positions).  For now, the default (0) is
      to warn about non-zero file position use, but retain the legacy
      behavior.  Setting this to -1 disables the warning, and setting this to
      1 enables the file position respecting behavior.
      [akpm@linux-foundation.org: fix build]
      [akpm@linux-foundation.org: move misplaced hunk, per Randy]
      Signed-off-by: default avatarKees Cook <keescook@chromium.org>
      Cc: Randy Dunlap <rdunlap@infradead.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  4. 07 Apr, 2014 1 commit
  5. 13 Mar, 2014 1 commit
    • Mathieu Desnoyers's avatar
      Fix: module signature vs tracepoints: add new TAINT_UNSIGNED_MODULE · 66cc69e3
      Mathieu Desnoyers authored
      Users have reported being unable to trace non-signed modules loaded
      within a kernel supporting module signature.
      This is caused by tracepoint.c:tracepoint_module_coming() refusing to
      take into account tracepoints sitting within force-loaded modules
      (TAINT_FORCED_MODULE). The reason for this check, in the first place, is
      that a force-loaded module may have a struct module incompatible with
      the layout expected by the kernel, and can thus cause a kernel crash
      upon forced load of that module on a kernel with CONFIG_TRACEPOINTS=y.
      Tracepoints, however, specifically accept TAINT_OOT_MODULE and
      TAINT_CRAP, since those modules do not lead to the "very likely system
      crash" issue cited above for force-loaded modules.
      With kernels having CONFIG_MODULE_SIG=y (signed modules), a non-signed
      module is tainted re-using the TAINT_FORCED_MODULE taint flag.
      Unfortunately, this means that Tracepoints treat that module as a
      force-loaded module, and thus silently refuse to consider any tracepoint
      within this module.
      Since an unsigned module does not fit within the "very likely system
      crash" category of tainting, add a new TAINT_UNSIGNED_MODULE taint flag
      to specifically address this taint behavior, and accept those modules
      within Tracepoints. We use the letter 'X' as a taint flag character for
      a module being loaded that doesn't know how to sign its name (proposed
      by Steven Rostedt).
      Also add the missing 'O' entry to trace event show_module_flags() list
      for the sake of completeness.
      Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
      Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      NAKed-by: default avatarIngo Molnar <mingo@redhat.com>
      CC: Thomas Gleixner <tglx@linutronix.de>
      CC: David Howells <dhowells@redhat.com>
      CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
  6. 31 Jan, 2014 1 commit
  7. 28 Jan, 2014 1 commit
  8. 25 Jan, 2014 1 commit
  9. 24 Jan, 2014 1 commit
    • Kees Cook's avatar
      kexec: add sysctl to disable kexec_load · 7984754b
      Kees Cook authored
      For general-purpose (i.e.  distro) kernel builds it makes sense to build
      with CONFIG_KEXEC to allow end users to choose what kind of things they
      want to do with kexec.  However, in the face of trying to lock down a
      system with such a kernel, there needs to be a way to disable kexec_load
      (much like module loading can be disabled).  Without this, it is too easy
      for the root user to modify kernel memory even when CONFIG_STRICT_DEVMEM
      and modules_disabled are set.  With this change, it is still possible to
      load an image for use later, then disable kexec_load so the image (or lack
      of image) can't be altered.
      The intention is for using this in environments where "perfect"
      enforcement is hard.  Without a verified boot, along with verified
      modules, and along with verified kexec, this is trying to give a system a
      better chance to defend itself (or at least grow the window of
      discoverability) against attack in the face of a privilege escalation.
      In my mind, I consider several boot scenarios:
      1) Verified boot of read-only verified root fs loading fd-based
         verification of kexec images.
      2) Secure boot of writable root fs loading signed kexec images.
      3) Regular boot loading kexec (e.g. kcrash) image early and locking it.
      4) Regular boot with no control of kexec image at all.
      1 and 2 don't exist yet, but will soon once the verified kexec series has
      landed.  4 is the state of things now.  The gap between 2 and 4 is too
      large, so this change creates scenario 3, a middle-ground above 4 when 2
      and 1 are not possible for a system.
      Signed-off-by: default avatarKees Cook <keescook@chromium.org>
      Acked-by: default avatarRik van Riel <riel@redhat.com>
      Cc: Vivek Goyal <vgoyal@redhat.com>
      Cc: Eric Biederman <ebiederm@xmission.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  10. 17 Dec, 2013 1 commit
  11. 13 Nov, 2013 1 commit
    • Ryan Mallon's avatar
      vsprintf: check real user/group id for %pK · 312b4e22
      Ryan Mallon authored
      Some setuid binaries will allow reading of files which have read
      permission by the real user id.  This is problematic with files which
      use %pK because the file access permission is checked at open() time,
      but the kptr_restrict setting is checked at read() time.  If a setuid
      binary opens a %pK file as an unprivileged user, and then elevates
      permissions before reading the file, then kernel pointer values may be
      This happens for example with the setuid pppd application on Ubuntu 12.04:
        $ head -1 /proc/kallsyms
        00000000 T startup_32
        $ pppd file /proc/kallsyms
        pppd: In file /proc/kallsyms: unrecognized option 'c1000000'
      This will only leak the pointer value from the first line, but other
      setuid binaries may leak more information.
      Fix this by adding a check that in addition to the current process having
      CAP_SYSLOG, that effective user and group ids are equal to the real ids.
      If a setuid binary reads the contents of a file which uses %pK then the
      pointer values will be printed as NULL if the real user is unprivileged.
      Update the sysctl documentation to reflect the changes, and also correct
      the documentation to state the kptr_restrict=0 is the default.
      This is a only temporary solution to the issue.  The correct solution is
      to do the permission check at open() time on files, and to replace %pK
      with a function which checks the open() time permission.  %pK uses in
      printk should be removed since no sane permission check can be done, and
      instead protected by using dmesg_restrict.
      Signed-off-by: default avatarRyan Mallon <rmallon@gmail.com>
      Cc: Kees Cook <keescook@chromium.org>
      Cc: Alexander Viro <viro@zeniv.linux.org.uk>
      Cc: Joe Perches <joe@perches.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: <stable@vger.kernel.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  12. 09 Oct, 2013 5 commits
  13. 11 Sep, 2013 1 commit
  14. 23 Jun, 2013 1 commit
    • Dave Hansen's avatar
      perf: Drop sample rate when sampling is too slow · 14c63f17
      Dave Hansen authored
      This patch keeps track of how long perf's NMI handler is taking,
      and also calculates how many samples perf can take a second.  If
      the sample length times the expected max number of samples
      exceeds a configurable threshold, it drops the sample rate.
      This way, we don't have a runaway sampling process eating up the
      This patch can tend to drop the sample rate down to level where
      perf doesn't work very well.  *BUT* the alternative is that my
      system hangs because it spends all of its time handling NMIs.
      I'll take a busted performance tool over an entire system that's
      busted and undebuggable any day.
      BTW, my suspicion is that there's still an underlying bug here.
      Using the HPET instead of the TSC is definitely a contributing
      factor, but I suspect there are some other things going on.
      But, I can't go dig down on a bug like that with my machine
      hanging all the time.
      Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
      Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: paulus@samba.org
      Cc: acme@ghostprotocols.net
      Cc: Dave Hansen <dave@sr71.net>
      [ Prettified it a bit. ]
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
  15. 28 May, 2013 2 commits
  16. 05 Jan, 2013 2 commits
  17. 05 Oct, 2012 1 commit
  18. 07 Feb, 2012 1 commit
  19. 13 Jan, 2012 1 commit
  20. 05 Dec, 2011 1 commit
  21. 01 Nov, 2011 1 commit
    • Dan Ballard's avatar
      kernel/sysctl.c: add cap_last_cap to /proc/sys/kernel · 73efc039
      Dan Ballard authored
      Userspace needs to know the highest valid capability of the running
      kernel, which right now cannot reliably be retrieved from the header files
      only.  The fact that this value cannot be determined properly right now
      creates various problems for libraries compiled on newer header files
      which are run on older kernels.  They assume capabilities are available
      which actually aren't.  libcap-ng is one example.  And we ran into the
      same problem with systemd too.
      Now the capability is exported in /proc/sys/kernel/cap_last_cap.
      [akpm@linux-foundation.org: make cap_last_cap const, per Ulrich]
      Signed-off-by: default avatarDan Ballard <dan@mindstab.net>
      Cc: Randy Dunlap <rdunlap@xenotime.net>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Lennart Poettering <lennart@poettering.net>
      Cc: Kay Sievers <kay.sievers@vrfy.org>
      Cc: Ulrich Drepper <drepper@akkadia.org>
      Cc: James Morris <jmorris@namei.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  22. 26 Jul, 2011 1 commit
    • Vasiliy Kulikov's avatar
      ipc: introduce shm_rmid_forced sysctl · b34a6b1d
      Vasiliy Kulikov authored
      Add support for the shm_rmid_forced sysctl.  If set to 1, all shared
      memory objects in current ipc namespace will be automatically forced to
      use IPC_RMID.
      The POSIX way of handling shmem allows one to create shm objects and
      call shmdt(), leaving shm object associated with no process, thus
      consuming memory not counted via rlimits.
      With shm_rmid_forced=1 the shared memory object is counted at least for
      one process, so OOM killer may effectively kill the fat process holding
      the shared memory.
      It obviously breaks POSIX - some programs relying on the feature would
      stop working.  So set shm_rmid_forced=1 only if you're sure nobody uses
      "orphaned" memory.  Use shm_rmid_forced=0 by default for compatability
      The feature was previously impemented in -ow as a configure option.
      [akpm@linux-foundation.org: fix documentation, per Randy]
      [akpm@linux-foundation.org: fix warning]
      [akpm@linux-foundation.org: readability/conventionality tweaks]
      [akpm@linux-foundation.org: fix shm_rmid_forced/shm_forced_rmid confusion, use standard comment layout]
      Signed-off-by: default avatarVasiliy Kulikov <segoon@openwall.com>
      Cc: Randy Dunlap <rdunlap@xenotime.net>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: "Serge E. Hallyn" <serge.hallyn@canonical.com>
      Cc: Daniel Lezcano <daniel.lezcano@free.fr>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Tejun Heo <tj@kernel.org>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
      Cc: Solar Designer <solar@openwall.com>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  23. 23 Jul, 2011 1 commit
  24. 27 May, 2011 1 commit
    • Jiri Slaby's avatar
      coredump: add support for exe_file in core name · 57cc083a
      Jiri Slaby authored
      Now, exe_file is not proc FS dependent, so we can use it to name core
      file.  So we add %E pattern for core file name cration which extract path
      from mm_struct->exe_file.  Then it converts slashes to exclamation marks
      and pastes the result to the core file name itself.
      This is useful for environments where binary names are longer than 16
      character (the current->comm limitation).  Also where there are binaries
      with same name but in a different path.  Further in case the binery itself
      changes its current->comm after exec.
      So by doing (s/$/#/ -- # is treated as git comment):
        $ sysctl kernel.core_pattern='core.%p.%e.%E'
        $ ln /bin/cat cat45678901234567890
        $ ./cat45678901234567890
        $ rm cat45678901234567890
        $ fg
        ^\Quit (core dumped)
        $ ls core*
      we now get:
        core.2434.cat456789012345.!root!cat45678901234567890 (deleted)
      Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
      Cc: Al Viro <viro@zeniv.linux.org.uk>
      Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
      Reviewed-by: default avatarAndi Kleen <andi@firstfloor.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  25. 11 Feb, 2011 1 commit
  26. 13 Jan, 2011 1 commit
    • Dan Rosenberg's avatar
      kptr_restrict for hiding kernel pointers from unprivileged users · 455cd5ab
      Dan Rosenberg authored
      Add the %pK printk format specifier and the /proc/sys/kernel/kptr_restrict
      The %pK format specifier is designed to hide exposed kernel pointers,
      specifically via /proc interfaces.  Exposing these pointers provides an
      easy target for kernel write vulnerabilities, since they reveal the
      locations of writable structures containing easily triggerable function
      pointers.  The behavior of %pK depends on the kptr_restrict sysctl.
      If kptr_restrict is set to 0, no deviation from the standard %p behavior
      occurs.  If kptr_restrict is set to 1, the default, if the current user
      (intended to be a reader via seq_printf(), etc.) does not have CAP_SYSLOG
      (currently in the LSM tree), kernel pointers using %pK are printed as 0's.
       If kptr_restrict is set to 2, kernel pointers using %pK are printed as
      0's regardless of privileges.  Replacing with 0's was chosen over the
      default "(null)", which cannot be parsed by userland %p, which expects
      [akpm@linux-foundation.org: check for IRQ context when !kptr_restrict, save an indent level, s/WARN/WARN_ONCE/]
      [akpm@linux-foundation.org: coding-style fixup]
      [randy.dunlap@oracle.com: fix kernel/sysctl.c warning]
      Signed-off-by: default avatarDan Rosenberg <drosenberg@vsecurity.com>
      Signed-off-by: default avatarRandy Dunlap <randy.dunlap@oracle.com>
      Cc: James Morris <jmorris@namei.org>
      Cc: Eric Dumazet <eric.dumazet@gmail.com>
      Cc: Thomas Graf <tgraf@infradead.org>
      Cc: Eugene Teo <eugeneteo@kernel.org>
      Cc: Kees Cook <kees.cook@canonical.com>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: David S. Miller <davem@davemloft.net>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Eric Paris <eparis@parisplace.org>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  27. 08 Dec, 2010 1 commit
  28. 12 Nov, 2010 1 commit
  29. 11 Dec, 2009 1 commit
  30. 09 Nov, 2009 1 commit
  31. 24 Sep, 2009 1 commit
    • Neil Horman's avatar
      exec: let do_coredump() limit the number of concurrent dumps to pipes · a293980c
      Neil Horman authored
      Introduce core pipe limiting sysctl.
      Since we can dump cores to pipe, rather than directly to the filesystem,
      we create a condition in which a user can create a very high load on the
      system simply by running bad applications.
      If the pipe reader specified in core_pattern is poorly written, we can
      have lots of ourstandig resources and processes in the system.
      This sysctl introduces an ability to limit that resource consumption.
      core_pipe_limit defines how many in-flight dumps may be run in parallel,
      dumps beyond this value are skipped and a note is made in the kernel log.
      A special value of 0 in core_pipe_limit denotes unlimited core dumps may
      be handled (this is the default value).
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: default avatarNeil Horman <nhorman@tuxdriver.com>
      Reported-by: default avatarEarl Chew <earl_chew@agilent.com>
      Cc: Oleg Nesterov <oleg@tv-sign.ru>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  32. 23 Sep, 2009 1 commit
  33. 21 Sep, 2009 1 commit
  34. 11 Sep, 2009 1 commit