kernel/linux.git/include/linux/psi.h, branch v6.6.132

sched/psi: use kernfs polling functions for PSI trigger polling

2023-07-10T07:52:30+00:00

Destroying psi trigger in cgroup_file_release causes UAF issues when a cgroup is removed from under a polling process. This is happening because cgroup removal causes a call to cgroup_file_release while the actual file is still alive. Destroying the trigger at this point would also destroy its waitqueue head and if there is still a polling process on that file accessing the waitqueue, it will step on the freed pointer: do_select vfs_poll do_rmdir cgroup_rmdir kernfs_drain_open_files cgroup_file_release cgroup_pressure_release psi_trigger_destroy wake_up_pollfree(&t->event_wait) // vfs_poll is unblocked synchronize_rcu kfree(t) poll_freewait -> UAF access to the trigger's waitqueue head Patch [1] fixed this issue for epoll() case using wake_up_pollfree(), however the same issue exists for synchronous poll() case. The root cause of this issue is that the lifecycles of the psi trigger's waitqueue and of the file associated with the trigger are different. Fix this by using kernfs_generic_poll function when polling on cgroup-specific psi triggers. It internally uses kernfs_open_node->poll waitqueue head with its lifecycle tied to the file's lifecycle. This also renders the fix in [1] obsolete, so revert it. [1] commit c2dbe32d5db5 ("sched/psi: Fix use-after-free in ep_remove_wait_queue()") Fixes: 0e94682b73bf ("psi: introduce psi monitor") Closes: https://lore.kernel.org/all/20230613062306.101831-1-lujialin4@huawei.com/ Reported-by: Lu Jialin Signed-off-by: Suren Baghdasaryan Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20230630005612.1014540-1-surenb@google.com

sched/psi: Allow unprivileged polling of N*2s period

2023-04-05T07:58:50+00:00

PSI offers 2 mechanisms to get information about a specific resource pressure. One is reading from /proc/pressure/, which gives average pressures aggregated every 2s. The other is creating a pollable fd for a specific resource and cgroup. The trigger creation requires CAP_SYS_RESOURCE, and gives the possibility to pick specific time window and threshold, spawing an RT thread to aggregate the data. Systemd would like to provide containers the option to monitor pressure on their own cgroup and sub-cgroups. For example, if systemd launches a container that itself then launches services, the container should have the ability to poll() for pressure in individual services. But neither the container nor the services are privileged. This patch implements a mechanism to allow unprivileged users to create pressure triggers. The difference with privileged triggers creation is that unprivileged ones must have a time window that's a multiple of 2s. This is so that we can avoid unrestricted spawning of rt threads, and use instead the same aggregation mechanism done for the averages, which runs independently of any triggers. Suggested-by: Johannes Weiner Signed-off-by: Domenico Cerasuolo Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lore.kernel.org/r/20230330105418.77061-5-cerasuolodomenico@gmail.com

sched/psi: Per-cgroup PSI accounting disable/re-enable interface

2022-09-09T09:08:33+00:00

PSI accounts stalls for each cgroup separately and aggregates it at each level of the hierarchy. This may cause non-negligible overhead for some workloads when under deep level of the hierarchy. commit 3958e2d0c34e ("cgroup: make per-cgroup pressure stall tracking configurable") make PSI to skip per-cgroup stall accounting, only account system-wide to avoid this each level overhead. But for our use case, we also want leaf cgroup PSI stats accounted for userspace adjustment on that cgroup, apart from only system-wide adjustment. So this patch introduce a per-cgroup PSI accounting disable/re-enable interface "cgroup.pressure", which is a read-write single value file that allowed values are "0" and "1", the defaults is "1" so per-cgroup PSI stats is enabled by default. Implementation details: It should be relatively straight-forward to disable and re-enable state aggregation, time tracking, averaging on a per-cgroup level, if we can live with losing history from while it was disabled. I.e. the avgs will restart from 0, total= will have gaps. But it's hard or complex to stop/restart groupc->tasks[] updates, which is not implemented in this patch. So we always update groupc->tasks[] and PSI_ONCPU bit in psi_group_change() even when the cgroup PSI stats is disabled. Suggested-by: Johannes Weiner Suggested-by: Tejun Heo Signed-off-by: Chengming Zhou Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lkml.kernel.org/r/20220907090332.2078-1-zhouchengming@bytedance.com

sched/psi: Consolidate cgroup_psi()

2022-09-09T09:08:33+00:00

cgroup_psi() can't return psi_group for root cgroup, so we have many open code "psi = cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi". This patch move cgroup_psi() definition to , in which we can return psi_system for root cgroup, so can handle all cgroups. Signed-off-by: Chengming Zhou Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lore.kernel.org/r/20220825164111.29534-9-zhouchengming@bytedance.com

sched/psi: Move private helpers to sched/stats.h

2022-09-09T09:08:31+00:00

This patch move psi_task_change/psi_task_switch declarations out of PSI public header, since they are only needed for implementing the PSI stats tracking in sched/stats.h psi_task_switch is obvious, psi_task_change can't be public helper since it doesn't check psi_disabled static key. And there is no any user now, so put it in sched/stats.h too. Signed-off-by: Chengming Zhou Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lore.kernel.org/r/20220825164111.29534-5-zhouchengming@bytedance.com

sched/psi: Remove unused parameter nbytes of psi_trigger_create()

2022-08-15T22:35:25+00:00

psi_trigger_create()'s 'nbytes' parameter is not used, so we can remove it. Signed-off-by: Hao Jia Reviewed-by: Ingo Molnar Acked-by: Johannes Weiner Signed-off-by: Tejun Heo

headers/prep: Fix header to build standalone:

2022-03-21T10:13:49+00:00

Add the dependency to , because cgroup_move_task() will dereference 'struct css_set'. ( Only older toolchains are affected, due to variations in the implementation of rcu_assign_pointer() et al. ) Cc: Peter Zijlstra Cc: Linus Torvalds Reported-by: Sachin Sant Reported-by: Andrew Morton Reported-by: Borislav Petkov Signed-off-by: Ingo Molnar

psi: fix "no previous prototype" warnings when CONFIG_CGROUPS=n

2022-01-30T07:56:58+00:00

When CONFIG_CGROUPS is disabled psi code generates the following warnings: kernel/sched/psi.c:1112:21: warning: no previous prototype for 'psi_trigger_create' [-Wmissing-prototypes] 1112 | struct psi_trigger *psi_trigger_create(struct psi_group *group, | ^~~~~~~~~~~~~~~~~~ kernel/sched/psi.c:1182:6: warning: no previous prototype for 'psi_trigger_destroy' [-Wmissing-prototypes] 1182 | void psi_trigger_destroy(struct psi_trigger *t) | ^~~~~~~~~~~~~~~~~~~ kernel/sched/psi.c:1249:10: warning: no previous prototype for 'psi_trigger_poll' [-Wmissing-prototypes] 1249 | __poll_t psi_trigger_poll(void **trigger_ptr, | ^~~~~~~~~~~~~~~~ Change the declarations of these functions in the header to provide the prototypes even when they are unused. Link: https://lkml.kernel.org/r/20220119223940.787748-2-surenb@google.com Fixes: 0e94682b73bf ("psi: introduce psi monitor") Signed-off-by: Suren Baghdasaryan Reported-by: kernel test robot Acked-by: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

psi: Fix uaf issue when psi trigger is destroyed while being polled

2022-01-18T11:09:57+00:00

With write operation on psi files replacing old trigger with a new one, the lifetime of its waitqueue is totally arbitrary. Overwriting an existing trigger causes its waitqueue to be freed and pending poll() will stumble on trigger->event_wait which was destroyed. Fix this by disallowing to redefine an existing psi trigger. If a write operation is used on a file descriptor with an already existing psi trigger, the operation will fail with EBUSY error. Also bypass a check for psi_disabled in the psi_trigger_destroy as the flag can be flipped after the trigger is created, leading to a memory leak. Fixes: 0e94682b73bf ("psi: introduce psi monitor") Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com Suggested-by: Linus Torvalds Analyzed-by: Eric Biggers Signed-off-by: Suren Baghdasaryan Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Eric Biggers Acked-by: Johannes Weiner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220111232309.1786347-1-surenb@google.com

psi: Add a missing SPDX license header

2021-11-17T13:48:59+00:00

Add the missing SPDX license header to include/linux/psi.h include/linux/psi_types.h kernel/sched/psi.c Signed-off-by: Liu Xinpeng Signed-off-by: Peter Zijlstra (Intel) Acked-by: Johannes Weiner Link: https://lore.kernel.org/r/1635133586-84611-2-git-send-email-liuxp11@chinatelecom.cn