From: Chris Hyser chris.hyser@oracle.com
mainline inclusion from mainline-v5.14-rc1 commit 7ac592aa35a684ff1858fb9ec282886b9e3575ac category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5OOWG CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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This patch provides support for setting and copying core scheduling 'task cookies' between threads (PID), processes (TGID), and process groups (PGID).
The value of core scheduling isn't that tasks don't share a core, 'nosmt' can do that. The value lies in exploiting all the sharing opportunities that exist to recover possible lost performance and that requires a degree of flexibility in the API.
From a security perspective (and there are others), the thread, process and process group distinction is an existent hierarchal categorization of tasks that reflects many of the security concerns about 'data sharing'. For example, protecting against cache-snooping by a thread that can just read the memory directly isn't all that useful.
With this in mind, subcommands to CREATE/SHARE (TO/FROM) provide a mechanism to create and share cookies. CREATE/SHARE_TO specify a target pid with enum pidtype used to specify the scope of the targeted tasks. For example, PIDTYPE_TGID will share the cookie with the process and all of it's threads as typically desired in a security scenario.
API:
prctl(PR_SCHED_CORE, PR_SCHED_CORE_GET, tgtpid, pidtype, &cookie) prctl(PR_SCHED_CORE, PR_SCHED_CORE_CREATE, tgtpid, pidtype, NULL) prctl(PR_SCHED_CORE, PR_SCHED_CORE_SHARE_TO, tgtpid, pidtype, NULL) prctl(PR_SCHED_CORE, PR_SCHED_CORE_SHARE_FROM, srcpid, pidtype, NULL)
where 'tgtpid/srcpid == 0' implies the current process and pidtype is kernel enum pid_type {PIDTYPE_PID, PIDTYPE_TGID, PIDTYPE_PGID, ...}.
For return values, EINVAL, ENOMEM are what they say. ESRCH means the tgtpid/srcpid was not found. EPERM indicates lack of PTRACE permission access to tgtpid/srcpid. ENODEV indicates your machines lacks SMT.
[peterz: complete rewrite] Signed-off-by: Chris Hyser chris.hyser@oracle.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Tested-by: Don Hiatt dhiatt@digitalocean.com Tested-by: Hongyu Ning hongyu.ning@linux.intel.com Tested-by: Vincent Guittot vincent.guittot@linaro.org Link: https://lkml.kernel.org/r/20210422123309.039845339@infradead.org Signed-off-by: Lin Shengwang linshengwang1@huawei.com Reviewed-by: lihua hucool.lihua@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- include/linux/sched.h | 2 + include/uapi/linux/prctl.h | 8 +++ kernel/sched/core_sched.c | 114 +++++++++++++++++++++++++++++++ kernel/sys.c | 5 ++ tools/include/uapi/linux/prctl.h | 8 +++ 5 files changed, 137 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h index a133a67a1b86..ea82fb089cd1 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2176,6 +2176,8 @@ const struct cpumask *sched_trace_rd_span(struct root_domain *rd); #ifdef CONFIG_SCHED_CORE extern void sched_core_free(struct task_struct *tsk); extern void sched_core_fork(struct task_struct *p); +extern int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type, + unsigned long uaddr); #else static inline void sched_core_free(struct task_struct *tsk) { } static inline void sched_core_fork(struct task_struct *p) { } diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 7f0827705c9a..892da2795b59 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -247,4 +247,12 @@ struct prctl_mm_map { #define PR_SET_IO_FLUSHER 57 #define PR_GET_IO_FLUSHER 58
+/* Request the scheduler to share a core */ +#define PR_SCHED_CORE 62 +# define PR_SCHED_CORE_GET 0 +# define PR_SCHED_CORE_CREATE 1 /* create unique core_sched cookie */ +# define PR_SCHED_CORE_SHARE_TO 2 /* push core_sched cookie to pid */ +# define PR_SCHED_CORE_SHARE_FROM 3 /* pull core_sched cookie to pid */ +# define PR_SCHED_CORE_MAX 4 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sched/core_sched.c b/kernel/sched/core_sched.c index dcbbeaefaaa3..9a80e9a474c0 100644 --- a/kernel/sched/core_sched.c +++ b/kernel/sched/core_sched.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0-only
+#include <linux/prctl.h> #include "sched.h"
/* @@ -113,3 +114,116 @@ void sched_core_free(struct task_struct *p) { sched_core_put_cookie(p->core_cookie); } + +static void __sched_core_set(struct task_struct *p, unsigned long cookie) +{ + cookie = sched_core_get_cookie(cookie); + cookie = sched_core_update_cookie(p, cookie); + sched_core_put_cookie(cookie); +} + +/* Called from prctl interface: PR_SCHED_CORE */ +int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type, + unsigned long uaddr) +{ + unsigned long cookie = 0, id = 0; + struct task_struct *task, *p; + struct pid *grp; + int err = 0; + + if (!static_branch_likely(&sched_smt_present)) + return -ENODEV; + + if (type > PIDTYPE_PGID || cmd >= PR_SCHED_CORE_MAX || pid < 0 || + (cmd != PR_SCHED_CORE_GET && uaddr)) + return -EINVAL; + + rcu_read_lock(); + if (pid == 0) { + task = current; + } else { + task = find_task_by_vpid(pid); + if (!task) { + rcu_read_unlock(); + return -ESRCH; + } + } + get_task_struct(task); + rcu_read_unlock(); + + /* + * Check if this process has the right to modify the specified + * process. Use the regular "ptrace_may_access()" checks. + */ + if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) { + err = -EPERM; + goto out; + } + + switch (cmd) { + case PR_SCHED_CORE_GET: + if (type != PIDTYPE_PID || uaddr & 7) { + err = -EINVAL; + goto out; + } + cookie = sched_core_clone_cookie(task); + if (cookie) { + /* XXX improve ? */ + ptr_to_hashval((void *)cookie, &id); + } + err = put_user(id, (u64 __user *)uaddr); + goto out; + + case PR_SCHED_CORE_CREATE: + cookie = sched_core_alloc_cookie(); + if (!cookie) { + err = -ENOMEM; + goto out; + } + break; + + case PR_SCHED_CORE_SHARE_TO: + cookie = sched_core_clone_cookie(current); + break; + + case PR_SCHED_CORE_SHARE_FROM: + if (type != PIDTYPE_PID) { + err = -EINVAL; + goto out; + } + cookie = sched_core_clone_cookie(task); + __sched_core_set(current, cookie); + goto out; + + default: + err = -EINVAL; + goto out; + }; + + if (type == PIDTYPE_PID) { + __sched_core_set(task, cookie); + goto out; + } + + read_lock(&tasklist_lock); + grp = task_pid_type(task, type); + + do_each_pid_thread(grp, type, p) { + if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) { + err = -EPERM; + goto out_tasklist; + } + } while_each_pid_thread(grp, type, p); + + do_each_pid_thread(grp, type, p) { + __sched_core_set(p, cookie); + } while_each_pid_thread(grp, type, p); +out_tasklist: + read_unlock(&tasklist_lock); + +out: + sched_core_put_cookie(cookie); + put_task_struct(task); + return err; +} + diff --git a/kernel/sys.c b/kernel/sys.c index 24a3a28ae228..c8a31e1037be 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2523,6 +2523,11 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
error = (current->flags & PR_IO_FLUSHER) == PR_IO_FLUSHER; break; +#ifdef CONFIG_SCHED_CORE + case PR_SCHED_CORE: + error = sched_core_share_pid(arg2, arg3, arg4, arg5); + break; +#endif default: error = -EINVAL; break; diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h index 7f0827705c9a..892da2795b59 100644 --- a/tools/include/uapi/linux/prctl.h +++ b/tools/include/uapi/linux/prctl.h @@ -247,4 +247,12 @@ struct prctl_mm_map { #define PR_SET_IO_FLUSHER 57 #define PR_GET_IO_FLUSHER 58
+/* Request the scheduler to share a core */ +#define PR_SCHED_CORE 62 +# define PR_SCHED_CORE_GET 0 +# define PR_SCHED_CORE_CREATE 1 /* create unique core_sched cookie */ +# define PR_SCHED_CORE_SHARE_TO 2 /* push core_sched cookie to pid */ +# define PR_SCHED_CORE_SHARE_FROM 3 /* pull core_sched cookie to pid */ +# define PR_SCHED_CORE_MAX 4 + #endif /* _LINUX_PRCTL_H */