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![Damien Le Moal](/assets/img/avatar_default.png)
The introduction of the macro IOPRIO_PRIO_LEVEL() in commiteca2040972
("scsi: block: ioprio: Clean up interface definition") results in an iopriority level to always be masked using the macro IOPRIO_LEVEL_MASK, and thus to the kernel always seeing an acceptable value for an I/O priority level when checked in ioprio_check_cap(). Before this patch, this function would return an error for some (but not all) invalid values for a level valid range of [0..7]. Restore and improve the detection of invalid priority levels by introducing the inline function ioprio_value() to check an ioprio class, level and hint value before combining these fields into a single value to be used with ioprio_set() or AIOs. If an invalid value for the class, level or hint of an ioprio is detected, ioprio_value() returns an ioprio using the class IOPRIO_CLASS_INVALID, indicating an invalid value and causing ioprio_check_cap() to return -EINVAL. Fixes:6c91325722
("scsi: block: Introduce ioprio hints") Fixes:eca2040972
("scsi: block: ioprio: Clean up interface definition") Signed-off-by: Damien Le Moal <dlemoal@kernel.org> Link: https://lore.kernel.org/r/20230608095556.124001-1-dlemoal@kernel.org Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
279 lines
5.8 KiB
C
279 lines
5.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* fs/ioprio.c
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*
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* Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
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*
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* Helper functions for setting/querying io priorities of processes. The
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* system calls closely mimmick getpriority/setpriority, see the man page for
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* those. The prio argument is a composite of prio class and prio data, where
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* the data argument has meaning within that class. The standard scheduling
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* classes have 8 distinct prio levels, with 0 being the highest prio and 7
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* being the lowest.
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*
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* IOW, setting BE scheduling class with prio 2 is done ala:
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*
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* unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
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*
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* ioprio_set(PRIO_PROCESS, pid, prio);
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*
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* See also Documentation/block/ioprio.rst
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*
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*/
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#include <linux/gfp.h>
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#include <linux/kernel.h>
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#include <linux/ioprio.h>
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#include <linux/cred.h>
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#include <linux/blkdev.h>
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#include <linux/capability.h>
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#include <linux/syscalls.h>
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#include <linux/security.h>
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#include <linux/pid_namespace.h>
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int ioprio_check_cap(int ioprio)
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{
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int class = IOPRIO_PRIO_CLASS(ioprio);
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int level = IOPRIO_PRIO_LEVEL(ioprio);
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switch (class) {
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case IOPRIO_CLASS_RT:
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/*
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* Originally this only checked for CAP_SYS_ADMIN,
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* which was implicitly allowed for pid 0 by security
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* modules such as SELinux. Make sure we check
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* CAP_SYS_ADMIN first to avoid a denial/avc for
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* possibly missing CAP_SYS_NICE permission.
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*/
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if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE))
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return -EPERM;
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fallthrough;
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/* rt has prio field too */
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case IOPRIO_CLASS_BE:
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if (level >= IOPRIO_NR_LEVELS)
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return -EINVAL;
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break;
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case IOPRIO_CLASS_IDLE:
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break;
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case IOPRIO_CLASS_NONE:
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if (level)
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return -EINVAL;
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break;
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case IOPRIO_CLASS_INVALID:
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default:
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return -EINVAL;
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}
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return 0;
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}
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SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
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{
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struct task_struct *p, *g;
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struct user_struct *user;
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struct pid *pgrp;
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kuid_t uid;
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int ret;
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ret = ioprio_check_cap(ioprio);
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if (ret)
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return ret;
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ret = -ESRCH;
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rcu_read_lock();
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switch (which) {
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case IOPRIO_WHO_PROCESS:
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if (!who)
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p = current;
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else
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p = find_task_by_vpid(who);
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if (p)
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ret = set_task_ioprio(p, ioprio);
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break;
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case IOPRIO_WHO_PGRP:
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if (!who)
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pgrp = task_pgrp(current);
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else
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pgrp = find_vpid(who);
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read_lock(&tasklist_lock);
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do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
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ret = set_task_ioprio(p, ioprio);
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if (ret) {
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read_unlock(&tasklist_lock);
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goto out;
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}
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} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
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read_unlock(&tasklist_lock);
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break;
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case IOPRIO_WHO_USER:
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uid = make_kuid(current_user_ns(), who);
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if (!uid_valid(uid))
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break;
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if (!who)
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user = current_user();
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else
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user = find_user(uid);
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if (!user)
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break;
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for_each_process_thread(g, p) {
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if (!uid_eq(task_uid(p), uid) ||
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!task_pid_vnr(p))
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continue;
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ret = set_task_ioprio(p, ioprio);
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if (ret)
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goto free_uid;
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}
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free_uid:
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if (who)
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free_uid(user);
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break;
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default:
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ret = -EINVAL;
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}
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out:
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rcu_read_unlock();
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return ret;
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}
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/*
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* If the task has set an I/O priority, use that. Otherwise, return
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* the default I/O priority.
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*
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* Expected to be called for current task or with task_lock() held to keep
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* io_context stable.
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*/
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int __get_task_ioprio(struct task_struct *p)
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{
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struct io_context *ioc = p->io_context;
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int prio;
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if (p != current)
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lockdep_assert_held(&p->alloc_lock);
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if (ioc)
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prio = ioc->ioprio;
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else
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prio = IOPRIO_DEFAULT;
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if (IOPRIO_PRIO_CLASS(prio) == IOPRIO_CLASS_NONE)
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prio = IOPRIO_PRIO_VALUE(task_nice_ioclass(p),
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task_nice_ioprio(p));
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return prio;
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}
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EXPORT_SYMBOL_GPL(__get_task_ioprio);
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static int get_task_ioprio(struct task_struct *p)
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{
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int ret;
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ret = security_task_getioprio(p);
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if (ret)
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goto out;
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task_lock(p);
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ret = __get_task_ioprio(p);
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task_unlock(p);
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out:
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return ret;
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}
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/*
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* Return raw IO priority value as set by userspace. We use this for
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* ioprio_get(pid, IOPRIO_WHO_PROCESS) so that we keep historical behavior and
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* also so that userspace can distinguish unset IO priority (which just gets
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* overriden based on task's nice value) from IO priority set to some value.
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*/
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static int get_task_raw_ioprio(struct task_struct *p)
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{
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int ret;
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ret = security_task_getioprio(p);
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if (ret)
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goto out;
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task_lock(p);
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if (p->io_context)
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ret = p->io_context->ioprio;
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else
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ret = IOPRIO_DEFAULT;
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task_unlock(p);
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out:
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return ret;
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}
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static int ioprio_best(unsigned short aprio, unsigned short bprio)
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{
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return min(aprio, bprio);
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}
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SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
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{
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struct task_struct *g, *p;
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struct user_struct *user;
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struct pid *pgrp;
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kuid_t uid;
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int ret = -ESRCH;
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int tmpio;
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rcu_read_lock();
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switch (which) {
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case IOPRIO_WHO_PROCESS:
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if (!who)
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p = current;
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else
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p = find_task_by_vpid(who);
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if (p)
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ret = get_task_raw_ioprio(p);
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break;
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case IOPRIO_WHO_PGRP:
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if (!who)
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pgrp = task_pgrp(current);
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else
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pgrp = find_vpid(who);
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read_lock(&tasklist_lock);
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do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
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tmpio = get_task_ioprio(p);
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if (tmpio < 0)
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continue;
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if (ret == -ESRCH)
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ret = tmpio;
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else
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ret = ioprio_best(ret, tmpio);
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} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
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read_unlock(&tasklist_lock);
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break;
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case IOPRIO_WHO_USER:
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uid = make_kuid(current_user_ns(), who);
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if (!who)
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user = current_user();
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else
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user = find_user(uid);
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if (!user)
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break;
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for_each_process_thread(g, p) {
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if (!uid_eq(task_uid(p), user->uid) ||
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!task_pid_vnr(p))
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continue;
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tmpio = get_task_ioprio(p);
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if (tmpio < 0)
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continue;
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if (ret == -ESRCH)
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ret = tmpio;
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else
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ret = ioprio_best(ret, tmpio);
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}
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if (who)
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free_uid(user);
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break;
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default:
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ret = -EINVAL;
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}
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rcu_read_unlock();
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return ret;
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}
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