user/sven/linux.git/include/linux/sched.h, branch v4.4.190

sched/fair: Don't free p->numa_faults with concurrent readers

2019-08-04T07:35:02Z

commit 16d51a590a8ce3befb1308e0e7ab77f3b661af33 upstream. When going through execve(), zero out the NUMA fault statistics instead of freeing them. During execve, the task is reachable through procfs and the scheduler. A concurrent /proc/*/sched reader can read data from a freed ->numa_faults allocation (confirmed by KASAN) and write it back to userspace. I believe that it would also be possible for a use-after-free read to occur through a race between a NUMA fault and execve(): task_numa_fault() can lead to task_numa_compare(), which invokes task_weight() on the currently running task of a different CPU. Another way to fix this would be to make ->numa_faults RCU-managed or add extra locking, but it seems easier to wipe the NUMA fault statistics on execve. Signed-off-by: Jann Horn Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Thomas Gleixner Cc: Will Deacon Fixes: 82727018b0d3 ("sched/numa: Call task_numa_free() from do_execve()") Link: https://lkml.kernel.org/r/20190716152047.14424-1-jannh@google.com Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

userfaultfd: don't pin the user memory in userfaultfd_file_create()

2019-06-11T10:24:11Z

commit d2005e3f41d4f9299e2df6a967c8beb5086967a9 upstream. userfaultfd_file_create() increments mm->mm_users; this means that the memory won't be unmapped/freed if mm owner exits/execs, and UFFDIO_COPY after that can populate the orphaned mm more. Change userfaultfd_file_create() and userfaultfd_ctx_put() to use mm->mm_count to pin mm_struct. This means that atomic_inc_not_zero(mm->mm_users) is needed when we are going to actually play with this memory. Except handle_userfault() path doesn't need this, the caller must already have a reference. The patch adds the new trivial helper, mmget_not_zero(), it can have more users. Link: http://lkml.kernel.org/r/20160516172254.GA8595@redhat.com Signed-off-by: Oleg Nesterov Cc: Andrea Arcangeli Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

x86/speculation: Add prctl() control for indirect branch speculation

2019-05-16T17:45:12Z

commit 9137bb27e60e554dab694eafa4cca241fa3a694f upstream. Add the PR_SPEC_INDIRECT_BRANCH option for the PR_GET_SPECULATION_CTRL and PR_SET_SPECULATION_CTRL prctls to allow fine grained per task control of indirect branch speculation via STIBP and IBPB. Invocations: Check indirect branch speculation status with - prctl(PR_GET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, 0, 0, 0); Enable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_ENABLE, 0, 0); Disable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_DISABLE, 0, 0); Force disable indirect branch speculation with - prctl(PR_SET_SPECULATION_CTRL, PR_SPEC_INDIRECT_BRANCH, PR_SPEC_FORCE_DISABLE, 0, 0); See Documentation/userspace-api/spec_ctrl.rst. Signed-off-by: Tim Chen Signed-off-by: Thomas Gleixner Reviewed-by: Ingo Molnar Cc: Peter Zijlstra Cc: Andy Lutomirski Cc: Linus Torvalds Cc: Jiri Kosina Cc: Tom Lendacky Cc: Josh Poimboeuf Cc: Andrea Arcangeli Cc: David Woodhouse Cc: Andi Kleen Cc: Dave Hansen Cc: Casey Schaufler Cc: Asit Mallick Cc: Arjan van de Ven Cc: Jon Masters Cc: Waiman Long Cc: Greg KH Cc: Dave Stewart Cc: Kees Cook Link: https://lkml.kernel.org/r/20181125185005.866780996@linutronix.de [bwh: Backported to 4.4: - Renumber the PFA flags - Drop changes in tools/include/uapi/linux/prctl.h - Adjust filename] Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman

exec: avoid gcc-8 warning for get_task_comm

2018-12-13T08:21:28Z

commit 3756f6401c302617c5e091081ca4d26ab604bec5 upstream. gcc-8 warns about using strncpy() with the source size as the limit: fs/exec.c:1223:32: error: argument to 'sizeof' in 'strncpy' call is the same expression as the source; did you mean to use the size of the destination? [-Werror=sizeof-pointer-memaccess] This is indeed slightly suspicious, as it protects us from source arguments without NUL-termination, but does not guarantee that the destination is terminated. This keeps the strncpy() to ensure we have properly padded target buffer, but ensures that we use the correct length, by passing the actual length of the destination buffer as well as adding a build-time check to ensure it is exactly TASK_COMM_LEN. There are only 23 callsites which I all reviewed to ensure this is currently the case. We could get away with doing only the check or passing the right length, but it doesn't hurt to do both. Link: http://lkml.kernel.org/r/20171205151724.1764896-1-arnd@arndb.de Signed-off-by: Arnd Bergmann Suggested-by: Kees Cook Acked-by: Kees Cook Acked-by: Ingo Molnar Cc: Alexander Viro Cc: Peter Zijlstra Cc: Serge Hallyn Cc: James Morris Cc: Aleksa Sarai Cc: "Eric W. Biederman" Cc: Frederic Weisbecker Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: get rid of vmacache_flush_all() entirely

2018-09-19T20:49:00Z

commit 7a9cdebdcc17e426fb5287e4a82db1dfe86339b2 upstream. Jann Horn points out that the vmacache_flush_all() function is not only potentially expensive, it's buggy too. It also happens to be entirely unnecessary, because the sequence number overflow case can be avoided by simply making the sequence number be 64-bit. That doesn't even grow the data structures in question, because the other adjacent fields are already 64-bit. So simplify the whole thing by just making the sequence number overflow case go away entirely, which gets rid of all the complications and makes the code faster too. Win-win. [ Oleg Nesterov points out that the VMACACHE_FULL_FLUSHES statistics also just goes away entirely with this ] Reported-by: Jann Horn Suggested-by: Will Deacon Acked-by: Davidlohr Bueso Cc: Oleg Nesterov Cc: stable@kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

prctl: Add force disable speculation

2018-07-25T08:18:27Z

commit 356e4bfff2c5489e016fdb925adbf12a1e3950ee upstream For certain use cases it is desired to enforce mitigations so they cannot be undone afterwards. That's important for loader stubs which want to prevent a child from disabling the mitigation again. Will also be used for seccomp(). The extra state preserving of the prctl state for SSB is a preparatory step for EBPF dymanic speculation control. Signed-off-by: Thomas Gleixner Signed-off-by: David Woodhouse Signed-off-by: Greg Kroah-Hartman Signed-off-by: Srivatsa S. Bhat Reviewed-by: Matt Helsley (VMware) Reviewed-by: Alexey Makhalov Reviewed-by: Bo Gan Signed-off-by: Greg Kroah-Hartman

sched/deadline: Use the revised wakeup rule for suspending constrained dl tasks

2018-01-31T11:06:07Z

commit 3effcb4247e74a51f5d8b775a1ee4abf87cc089a upstream. We have been facing some problems with self-suspending constrained deadline tasks. The main reason is that the original CBS was not designed for such sort of tasks. One problem reported by Xunlei Pang takes place when a task suspends, and then is awakened before the deadline, but so close to the deadline that its remaining runtime can cause the task to have an absolute density higher than allowed. In such situation, the original CBS assumes that the task is facing an early activation, and so it replenishes the task and set another deadline, one deadline in the future. This rule works fine for implicit deadline tasks. Moreover, it allows the system to adapt the period of a task in which the external event source suffered from a clock drift. However, this opens the window for bandwidth leakage for constrained deadline tasks. For instance, a task with the following parameters: runtime = 5 ms deadline = 7 ms [density] = 5 / 7 = 0.71 period = 1000 ms If the task runs for 1 ms, and then suspends for another 1ms, it will be awakened with the following parameters: remaining runtime = 4 laxity = 5 presenting a absolute density of 4 / 5 = 0.80. In this case, the original CBS would assume the task had an early wakeup. Then, CBS will reset the runtime, and the absolute deadline will be postponed by one relative deadline, allowing the task to run. The problem is that, if the task runs this pattern forever, it will keep receiving bandwidth, being able to run 1ms every 2ms. Following this behavior, the task would be able to run 500 ms in 1 sec. Thus running more than the 5 ms / 1 sec the admission control allowed it to run. Trying to address the self-suspending case, Luca Abeni, Giuseppe Lipari, and Juri Lelli [1] revisited the CBS in order to deal with self-suspending tasks. In the new approach, rather than replenishing/postponing the absolute deadline, the revised wakeup rule adjusts the remaining runtime, reducing it to fit into the allowed density. A revised version of the idea is: At a given time t, the maximum absolute density of a task cannot be higher than its relative density, that is: runtime / (deadline - t) <= dl_runtime / dl_deadline Knowing the laxity of a task (deadline - t), it is possible to move it to the other side of the equality, thus enabling to define max remaining runtime a task can use within the absolute deadline, without over-running the allowed density: runtime = (dl_runtime / dl_deadline) * (deadline - t) For instance, in our previous example, the task could still run: runtime = ( 5 / 7 ) * 5 runtime = 3.57 ms Without causing damage for other deadline tasks. It is note worthy that the laxity cannot be negative because that would cause a negative runtime. Thus, this patch depends on the patch: df8eac8cafce ("sched/deadline: Throttle a constrained deadline task activated after the deadline") Which throttles a constrained deadline task activated after the deadline. Finally, it is also possible to use the revised wakeup rule for all other tasks, but that would require some more discussions about pros and cons. [The main difference from the original commit is that the BW_SHIFT define was not present yet. As BW_SHIFT was introduced in a new feature, I just used the value (20), likewise we used to use before the #define. Other changes were required because of comments. - bistrot] Reported-by: Xunlei Pang Signed-off-by: Daniel Bristot de Oliveira [peterz: replaced dl_is_constrained with dl_is_implicit] Signed-off-by: Peter Zijlstra (Intel) Cc: Juri Lelli Cc: Linus Torvalds Cc: Luca Abeni Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Romulo Silva de Oliveira Cc: Steven Rostedt Cc: Thomas Gleixner Cc: Tommaso Cucinotta Link: http://lkml.kernel.org/r/5c800ab3a74a168a84ee5f3f84d12a02e11383be.1495803804.git.bristot@redhat.com Signed-off-by: Ingo Molnar Signed-off-by: Daniel Bristot de Oliveira Signed-off-by: Greg Kroah-Hartman

pids: make task_tgid_nr_ns() safe

2017-08-25T00:02:36Z

commit dd1c1f2f2028a7b851f701fc6a8ebe39dcb95e7c upstream. This was reported many times, and this was even mentioned in commit 52ee2dfdd4f5 ("pids: refactor vnr/nr_ns helpers to make them safe") but somehow nobody bothered to fix the obvious problem: task_tgid_nr_ns() is not safe because task->group_leader points to nowhere after the exiting task passes exit_notify(), rcu_read_lock() can not help. We really need to change __unhash_process() to nullify group_leader, parent, and real_parent, but this needs some cleanups. Until then we can turn task_tgid_nr_ns() into another user of __task_pid_nr_ns() and fix the problem. Reported-by: Troy Kensinger Signed-off-by: Oleg Nesterov Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

signal: protect SIGNAL_UNKILLABLE from unintentional clearing.

2017-08-11T16:08:59Z

[ Upstream commit 2d39b3cd34e6d323720d4c61bd714f5ae202c022 ] Since commit 00cd5c37afd5 ("ptrace: permit ptracing of /sbin/init") we can now trace init processes. init is initially protected with SIGNAL_UNKILLABLE which will prevent fatal signals such as SIGSTOP, but there are a number of paths during tracing where SIGNAL_UNKILLABLE can be implicitly cleared. This can result in init becoming stoppable/killable after tracing. For example, running: while true; do kill -STOP 1; done & strace -p 1 and then stopping strace and the kill loop will result in init being left in state TASK_STOPPED. Sending SIGCONT to init will resume it, but init will now respond to future SIGSTOP signals rather than ignoring them. Make sure that when setting SIGNAL_STOP_CONTINUED/SIGNAL_STOP_STOPPED that we don't clear SIGNAL_UNKILLABLE. Link: http://lkml.kernel.org/r/20170104122017.25047-1-jamie.iles@oracle.com Signed-off-by: Jamie Iles Acked-by: Oleg Nesterov Cc: Alexander Viro Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

cgroup, kthread: close race window where new kthreads can be migrated to non-root cgroups

2017-04-21T07:30:04Z

commit 77f88796cee819b9c4562b0b6b44691b3b7755b1 upstream. Creation of a kthread goes through a couple interlocked stages between the kthread itself and its creator. Once the new kthread starts running, it initializes itself and wakes up the creator. The creator then can further configure the kthread and then let it start doing its job by waking it up. In this configuration-by-creator stage, the creator is the only one that can wake it up but the kthread is visible to userland. When altering the kthread's attributes from userland is allowed, this is fine; however, for cases where CPU affinity is critical, kthread_bind() is used to first disable affinity changes from userland and then set the affinity. This also prevents the kthread from being migrated into non-root cgroups as that can affect the CPU affinity and many other things. Unfortunately, the cgroup side of protection is racy. While the PF_NO_SETAFFINITY flag prevents further migrations, userland can win the race before the creator sets the flag with kthread_bind() and put the kthread in a non-root cgroup, which can lead to all sorts of problems including incorrect CPU affinity and starvation. This bug got triggered by userland which periodically tries to migrate all processes in the root cpuset cgroup to a non-root one. Per-cpu workqueue workers got caught while being created and ended up with incorrected CPU affinity breaking concurrency management and sometimes stalling workqueue execution. This patch adds task->no_cgroup_migration which disallows the task to be migrated by userland. kthreadd starts with the flag set making every child kthread start in the root cgroup with migration disallowed. The flag is cleared after the kthread finishes initialization by which time PF_NO_SETAFFINITY is set if the kthread should stay in the root cgroup. It'd be better to wait for the initialization instead of failing but I couldn't think of a way of implementing that without adding either a new PF flag, or sleeping and retrying from waiting side. Even if userland depends on changing cgroup membership of a kthread, it either has to be synchronized with kthread_create() or periodically repeat, so it's unlikely that this would break anything. v2: Switch to a simpler implementation using a new task_struct bit field suggested by Oleg. Signed-off-by: Tejun Heo Suggested-by: Oleg Nesterov Cc: Linus Torvalds Cc: Andrew Morton Cc: Peter Zijlstra (Intel) Cc: Thomas Gleixner Reported-and-debugged-by: Chris Mason Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman