linux/kernel/signal.c, branch v4.5

signals: avoid random wakeups in sigsuspend()

2016-02-06T02:10:40Z

A random wakeup can get us out of sigsuspend() without TIF_SIGPENDING being set. Avoid that by making sure we were signaled, like sys_pause() does. Signed-off-by: Sasha Levin Acked-by: Oleg Nesterov Acked-by: Peter Zijlstra (Intel) Cc: Dmitry Vyukov Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kernel/signal.c: unexport sigsuspend()

2015-11-21T00:17:32Z

sigsuspend() is nowhere used except in signal.c itself, so we can mark it static do not pollute the global namespace. But this patch is more than a boring cleanup patch, it fixes a real issue on UserModeLinux. UML has a special console driver to display ttys using xterm, or other terminal emulators, on the host side. Vegard reported that sometimes UML is unable to spawn a xterm and he's facing the following warning: WARNING: CPU: 0 PID: 908 at include/linux/thread_info.h:128 sigsuspend+0xab/0xc0() It turned out that this warning makes absolutely no sense as the UML xterm code calls sigsuspend() on the host side, at least it tries. But as the kernel itself offers a sigsuspend() symbol the linker choose this one instead of the glibc wrapper. Interestingly this code used to work since ever but always blocked signals on the wrong side. Some recent kernel change made the WARN_ON() trigger and uncovered the bug. It is a wonderful example of how much works by chance on computers. :-) Fixes: 68f3f16d9ad0f1 ("new helper: sigsuspend()") Signed-off-by: Richard Weinberger Reported-by: Vegard Nossum Tested-by: Vegard Nossum Acked-by: Oleg Nesterov Cc: [3.5+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

coredump: ensure all coredumping tasks have SIGNAL_GROUP_COREDUMP

2015-11-07T01:50:42Z

task_will_free_mem() is wrong in many ways, and in particular the SIGNAL_GROUP_COREDUMP check is not reliable: a task can participate in the coredumping without SIGNAL_GROUP_COREDUMP bit set. change zap_threads() paths to always set SIGNAL_GROUP_COREDUMP even if other CLONE_VM processes can't react to SIGKILL. Fortunately, at least oom-kill case if fine; it kills all tasks sharing the same mm, so it should also kill the process which actually dumps the core. The change in prepare_signal() is not strictly necessary, it just ensures that the patch does not bring another subtle behavioural change. But it reminds us that this SIGNAL_GROUP_EXIT/COREDUMP case needs more changes. Signed-off-by: Oleg Nesterov Cc: David Rientjes Cc: Kyle Walker Acked-by: Michal Hocko Cc: Stanislav Kozina Cc: Tetsuo Handa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

signals: kill block_all_signals() and unblock_all_signals()

2015-11-07T01:50:42Z

It is hardly possible to enumerate all problems with block_all_signals() and unblock_all_signals(). Just for example, 1. block_all_signals(SIGSTOP/etc) simply can't help if the caller is multithreaded. Another thread can dequeue the signal and force the group stop. 2. Even is the caller is single-threaded, it will "stop" anyway. It will not sleep, but it will spin in kernel space until SIGCONT or SIGKILL. And a lot more. In short, this interface doesn't work at all, at least the last 10+ years. Daniel said: Yeah the only times I played around with the DRM_LOCK stuff was when old drivers accidentally deadlocked - my impression is that the entire DRM_LOCK thing was never really tested properly ;-) Hence I'm all for purging where this leaks out of the drm subsystem. Signed-off-by: Oleg Nesterov Acked-by: Daniel Vetter Acked-by: Dave Airlie Cc: Richard Weinberger Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

signal: fix information leak in copy_siginfo_to_user

2015-08-07T01:39:40Z

This function may copy the si_addr_lsb, si_lower and si_upper fields to user mode when they haven't been initialized, which can leak kernel stack data to user mode. Just checking the value of si_code is insufficient because the same si_code value is shared between multiple signals. This is solved by checking the value of si_signo in addition to si_code. Signed-off-by: Amanieu d'Antras Cc: Oleg Nesterov Cc: Ingo Molnar Cc: Russell King Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

signal: fix information leak in copy_siginfo_from_user32

2015-08-07T01:39:40Z

This function can leak kernel stack data when the user siginfo_t has a positive si_code value. The top 16 bits of si_code descibe which fields in the siginfo_t union are active, but they are treated inconsistently between copy_siginfo_from_user32, copy_siginfo_to_user32 and copy_siginfo_to_user. copy_siginfo_from_user32 is called from rt_sigqueueinfo and rt_tgsigqueueinfo in which the user has full control overthe top 16 bits of si_code. This fixes the following information leaks: x86: 8 bytes leaked when sending a signal from a 32-bit process to itself. This leak grows to 16 bytes if the process uses x32. (si_code = __SI_CHLD) x86: 100 bytes leaked when sending a signal from a 32-bit process to a 64-bit process. (si_code = -1) sparc: 4 bytes leaked when sending a signal from a 32-bit process to a 64-bit process. (si_code = any) parsic and s390 have similar bugs, but they are not vulnerable because rt_[tg]sigqueueinfo have checks that prevent sending a positive si_code to a different process. These bugs are also fixed for consistency. Signed-off-by: Amanieu d'Antras Cc: Oleg Nesterov Cc: Ingo Molnar Cc: Russell King Cc: Ralf Baechle Cc: Benjamin Herrenschmidt Cc: Chris Metcalf Cc: Paul Mackerras Cc: Michael Ellerman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security

2015-06-27T20:26:03Z

Pull security subsystem updates from James Morris: "The main change in this kernel is Casey's generalized LSM stacking work, which removes the hard-coding of Capabilities and Yama stacking, allowing multiple arbitrary "small" LSMs to be stacked with a default monolithic module (e.g. SELinux, Smack, AppArmor). See https://lwn.net/Articles/636056/ This will allow smaller, simpler LSMs to be incorporated into the mainline kernel and arbitrarily stacked by users. Also, this is a useful cleanup of the LSM code in its own right" * 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (38 commits) tpm, tpm_crb: fix le64_to_cpu conversions in crb_acpi_add() vTPM: set virtual device before passing to ibmvtpm_reset_crq tpm_ibmvtpm: remove unneccessary message level. ima: update builtin policies ima: extend "mask" policy matching support ima: add support for new "euid" policy condition ima: fix ima_show_template_data_ascii() Smack: freeing an error pointer in smk_write_revoke_subj() selinux: fix setting of security labels on NFS selinux: Remove unused permission definitions selinux: enable genfscon labeling for sysfs and pstore files selinux: enable per-file labeling for debugfs files. selinux: update netlink socket classes signals: don't abuse __flush_signals() in selinux_bprm_committed_creds() selinux: Print 'sclass' as string when unrecognized netlink message occurs Smack: allow multiple labels in onlycap Smack: fix seq operations in smackfs ima: pass iint to ima_add_violation() ima: wrap event related data to the new ima_event_data structure integrity: add validity checks for 'path' parameter ...

signals: don't abuse __flush_signals() in selinux_bprm_committed_creds()

2015-06-04T20:22:16Z

selinux_bprm_committed_creds()->__flush_signals() is not right, we shouldn't clear TIF_SIGPENDING unconditionally. There can be other reasons for signal_pending(): freezing(), JOBCTL_PENDING_MASK, and potentially more. Also change this code to check fatal_signal_pending() rather than SIGNAL_GROUP_EXIT, it looks a bit better. Now we can kill __flush_signals() before it finds another buggy user. Note: this code looks racy, we can flush a signal which was sent after the task SID has been updated. Signed-off-by: Oleg Nesterov Signed-off-by: Paul Moore

signals, sched: Change all uses of JOBCTL_* from 'int' to 'long'

2015-05-08T10:04:36Z

c56fb6564dcd ("Fix a misaligned load inside ptrace_attach()") makes jobctl an "unsigned long". It makes sense to have the masks applied to it match that type. This is currently just a cosmetic change, but it will prevent the mask from being unexpectedly truncated if we ever end up with masks with more bits. One instance of "signr" is an int, but I left this alone because the mask ensures that it will never overflow. Signed-off-by: Palmer Dabbelt Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Chris Metcalf Cc: Andrew Morton Cc: Borislav Petkov Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Thomas Gleixner Cc: bobby.prani@gmail.com Cc: oleg@redhat.com Cc: paulmck@linux.vnet.ibm.com Cc: richard@nod.at Cc: vdavydov@parallels.com Link: http://lkml.kernel.org/r/1430453997-32459-4-git-send-email-palmer@dabbelt.com Signed-off-by: Ingo Molnar

signal: remove warning about using SI_TKILL in rt_[tg]sigqueueinfo

2015-04-17T13:04:06Z

Sending SI_TKILL from rt_[tg]sigqueueinfo was deprecated, so now we issue a warning on the first attempt of doing it. We use WARN_ON_ONCE, which is not informative and, what is worse, taints the kernel, making the trinity syscall fuzzer complain false-positively from time to time. It does not look like we need this warning at all, because the behaviour changed quite a long time ago (2.6.39), and if an application relies on the old API, it gets EPERM anyway and can issue a warning by itself. So let us zap the warning in kernel. Signed-off-by: Vladimir Davydov Acked-by: Oleg Nesterov Cc: Richard Weinberger Cc: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds