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This introduces a per-filter flag (SECCOMP_FILTER_FLAG_WAIT_KILLABLE_RECV) that makes it so that when notifications are received by the supervisor the notifying process will transition to wait killable semantics. Although wait killable isn't a set of semantics formally exposed to userspace, the concept is searchable. If the notifying process is signaled prior to the notification being received by the userspace agent, it will be handled as normal. One quirk about how this is handled is that the notifying process only switches to TASK_KILLABLE if it receives a wakeup from either an addfd or a signal. This is to avoid an unnecessary wakeup of the notifying task. The reasons behind switching into wait_killable only after userspace receives the notification are: * Avoiding unncessary work - Often, workloads will perform work that they may abort (request racing comes to mind). This allows for syscalls to be aborted safely prior to the notification being received by the supervisor. In this, the supervisor doesn't end up doing work that the workload does not want to complete anyways. * Avoiding side effects - We don't want the syscall to be interruptible once the supervisor starts doing work because it may not be trivial to reverse the operation. For example, unmounting a file system may take a long time, and it's hard to rollback, or treat that as reentrant. * Avoid breaking runtimes - Various runtimes do not GC when they are during a syscall (or while running native code that subsequently calls a syscall). If many notifications are blocked, and not picked up by the supervisor, this can get the application into a bad state. Signed-off-by: Sargun Dhillon <sargun@sargun.me> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20220503080958.20220-2-sargun@sargun.me |
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| .. | ||
| accelerators | ||
| ebpf | ||
| ioctl | ||
| media | ||
| futex2.rst | ||
| index.rst | ||
| iommu.rst | ||
| landlock.rst | ||
| no_new_privs.rst | ||
| seccomp_filter.rst | ||
| spec_ctrl.rst | ||
| sysfs-platform_profile.rst | ||
| unshare.rst | ||
| vduse.rst | ||