mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 19:00:25 +00:00
![Omar Sandoval](/assets/img/avatar_default.png)
get_task_ioprio() accesses the task->io_context without holding the task lock and thus can race with exit_io_context(), leading to a use-after-free. The reproducer below hits this within a few seconds on my 4-core QEMU VM: #define _GNU_SOURCE #include <assert.h> #include <unistd.h> #include <sys/syscall.h> #include <sys/wait.h> int main(int argc, char **argv) { pid_t pid, child; long nproc, i; /* ioprio_set(IOPRIO_WHO_PROCESS, 0, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0)); */ syscall(SYS_ioprio_set, 1, 0, 0x6000); nproc = sysconf(_SC_NPROCESSORS_ONLN); for (i = 0; i < nproc; i++) { pid = fork(); assert(pid != -1); if (pid == 0) { for (;;) { pid = fork(); assert(pid != -1); if (pid == 0) { _exit(0); } else { child = wait(NULL); assert(child == pid); } } } pid = fork(); assert(pid != -1); if (pid == 0) { for (;;) { /* ioprio_get(IOPRIO_WHO_PGRP, 0); */ syscall(SYS_ioprio_get, 2, 0); } } } for (;;) { /* ioprio_get(IOPRIO_WHO_PGRP, 0); */ syscall(SYS_ioprio_get, 2, 0); } return 0; } This gets us KASAN dumps like this: [ 35.526914] ================================================================== [ 35.530009] BUG: KASAN: out-of-bounds in get_task_ioprio+0x7b/0x90 at addr ffff880066f34e6c [ 35.530009] Read of size 2 by task ioprio-gpf/363 [ 35.530009] ============================================================================= [ 35.530009] BUG blkdev_ioc (Not tainted): kasan: bad access detected [ 35.530009] ----------------------------------------------------------------------------- [ 35.530009] Disabling lock debugging due to kernel taint [ 35.530009] INFO: Allocated in create_task_io_context+0x2b/0x370 age=0 cpu=0 pid=360 [ 35.530009] ___slab_alloc+0x55d/0x5a0 [ 35.530009] __slab_alloc.isra.20+0x2b/0x40 [ 35.530009] kmem_cache_alloc_node+0x84/0x200 [ 35.530009] create_task_io_context+0x2b/0x370 [ 35.530009] get_task_io_context+0x92/0xb0 [ 35.530009] copy_process.part.8+0x5029/0x5660 [ 35.530009] _do_fork+0x155/0x7e0 [ 35.530009] SyS_clone+0x19/0x20 [ 35.530009] do_syscall_64+0x195/0x3a0 [ 35.530009] return_from_SYSCALL_64+0x0/0x6a [ 35.530009] INFO: Freed in put_io_context+0xe7/0x120 age=0 cpu=0 pid=1060 [ 35.530009] __slab_free+0x27b/0x3d0 [ 35.530009] kmem_cache_free+0x1fb/0x220 [ 35.530009] put_io_context+0xe7/0x120 [ 35.530009] put_io_context_active+0x238/0x380 [ 35.530009] exit_io_context+0x66/0x80 [ 35.530009] do_exit+0x158e/0x2b90 [ 35.530009] do_group_exit+0xe5/0x2b0 [ 35.530009] SyS_exit_group+0x1d/0x20 [ 35.530009] entry_SYSCALL_64_fastpath+0x1a/0xa4 [ 35.530009] INFO: Slab 0xffffea00019bcd00 objects=20 used=4 fp=0xffff880066f34ff0 flags=0x1fffe0000004080 [ 35.530009] INFO: Object 0xffff880066f34e58 @offset=3672 fp=0x0000000000000001 [ 35.530009] ================================================================== Fix it by grabbing the task lock while we poke at the io_context. Cc: stable@vger.kernel.org Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@fb.com>
247 lines
5.1 KiB
C
247 lines
5.1 KiB
C
/*
|
|
* fs/ioprio.c
|
|
*
|
|
* Copyright (C) 2004 Jens Axboe <axboe@kernel.dk>
|
|
*
|
|
* Helper functions for setting/querying io priorities of processes. The
|
|
* system calls closely mimmick getpriority/setpriority, see the man page for
|
|
* those. The prio argument is a composite of prio class and prio data, where
|
|
* the data argument has meaning within that class. The standard scheduling
|
|
* classes have 8 distinct prio levels, with 0 being the highest prio and 7
|
|
* being the lowest.
|
|
*
|
|
* IOW, setting BE scheduling class with prio 2 is done ala:
|
|
*
|
|
* unsigned int prio = (IOPRIO_CLASS_BE << IOPRIO_CLASS_SHIFT) | 2;
|
|
*
|
|
* ioprio_set(PRIO_PROCESS, pid, prio);
|
|
*
|
|
* See also Documentation/block/ioprio.txt
|
|
*
|
|
*/
|
|
#include <linux/gfp.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/export.h>
|
|
#include <linux/ioprio.h>
|
|
#include <linux/blkdev.h>
|
|
#include <linux/capability.h>
|
|
#include <linux/syscalls.h>
|
|
#include <linux/security.h>
|
|
#include <linux/pid_namespace.h>
|
|
|
|
int set_task_ioprio(struct task_struct *task, int ioprio)
|
|
{
|
|
int err;
|
|
struct io_context *ioc;
|
|
const struct cred *cred = current_cred(), *tcred;
|
|
|
|
rcu_read_lock();
|
|
tcred = __task_cred(task);
|
|
if (!uid_eq(tcred->uid, cred->euid) &&
|
|
!uid_eq(tcred->uid, cred->uid) && !capable(CAP_SYS_NICE)) {
|
|
rcu_read_unlock();
|
|
return -EPERM;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
err = security_task_setioprio(task, ioprio);
|
|
if (err)
|
|
return err;
|
|
|
|
ioc = get_task_io_context(task, GFP_ATOMIC, NUMA_NO_NODE);
|
|
if (ioc) {
|
|
ioc->ioprio = ioprio;
|
|
put_io_context(ioc);
|
|
}
|
|
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL_GPL(set_task_ioprio);
|
|
|
|
SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
|
|
{
|
|
int class = IOPRIO_PRIO_CLASS(ioprio);
|
|
int data = IOPRIO_PRIO_DATA(ioprio);
|
|
struct task_struct *p, *g;
|
|
struct user_struct *user;
|
|
struct pid *pgrp;
|
|
kuid_t uid;
|
|
int ret;
|
|
|
|
switch (class) {
|
|
case IOPRIO_CLASS_RT:
|
|
if (!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
/* fall through, rt has prio field too */
|
|
case IOPRIO_CLASS_BE:
|
|
if (data >= IOPRIO_BE_NR || data < 0)
|
|
return -EINVAL;
|
|
|
|
break;
|
|
case IOPRIO_CLASS_IDLE:
|
|
break;
|
|
case IOPRIO_CLASS_NONE:
|
|
if (data)
|
|
return -EINVAL;
|
|
break;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
|
|
ret = -ESRCH;
|
|
rcu_read_lock();
|
|
switch (which) {
|
|
case IOPRIO_WHO_PROCESS:
|
|
if (!who)
|
|
p = current;
|
|
else
|
|
p = find_task_by_vpid(who);
|
|
if (p)
|
|
ret = set_task_ioprio(p, ioprio);
|
|
break;
|
|
case IOPRIO_WHO_PGRP:
|
|
if (!who)
|
|
pgrp = task_pgrp(current);
|
|
else
|
|
pgrp = find_vpid(who);
|
|
do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
|
|
ret = set_task_ioprio(p, ioprio);
|
|
if (ret)
|
|
break;
|
|
} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
|
|
break;
|
|
case IOPRIO_WHO_USER:
|
|
uid = make_kuid(current_user_ns(), who);
|
|
if (!uid_valid(uid))
|
|
break;
|
|
if (!who)
|
|
user = current_user();
|
|
else
|
|
user = find_user(uid);
|
|
|
|
if (!user)
|
|
break;
|
|
|
|
do_each_thread(g, p) {
|
|
if (!uid_eq(task_uid(p), uid) ||
|
|
!task_pid_vnr(p))
|
|
continue;
|
|
ret = set_task_ioprio(p, ioprio);
|
|
if (ret)
|
|
goto free_uid;
|
|
} while_each_thread(g, p);
|
|
free_uid:
|
|
if (who)
|
|
free_uid(user);
|
|
break;
|
|
default:
|
|
ret = -EINVAL;
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|
|
|
|
static int get_task_ioprio(struct task_struct *p)
|
|
{
|
|
int ret;
|
|
|
|
ret = security_task_getioprio(p);
|
|
if (ret)
|
|
goto out;
|
|
ret = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, IOPRIO_NORM);
|
|
task_lock(p);
|
|
if (p->io_context)
|
|
ret = p->io_context->ioprio;
|
|
task_unlock(p);
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
int ioprio_best(unsigned short aprio, unsigned short bprio)
|
|
{
|
|
unsigned short aclass;
|
|
unsigned short bclass;
|
|
|
|
if (!ioprio_valid(aprio))
|
|
aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
|
|
if (!ioprio_valid(bprio))
|
|
bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);
|
|
|
|
aclass = IOPRIO_PRIO_CLASS(aprio);
|
|
bclass = IOPRIO_PRIO_CLASS(bprio);
|
|
if (aclass == bclass)
|
|
return min(aprio, bprio);
|
|
if (aclass > bclass)
|
|
return bprio;
|
|
else
|
|
return aprio;
|
|
}
|
|
|
|
SYSCALL_DEFINE2(ioprio_get, int, which, int, who)
|
|
{
|
|
struct task_struct *g, *p;
|
|
struct user_struct *user;
|
|
struct pid *pgrp;
|
|
kuid_t uid;
|
|
int ret = -ESRCH;
|
|
int tmpio;
|
|
|
|
rcu_read_lock();
|
|
switch (which) {
|
|
case IOPRIO_WHO_PROCESS:
|
|
if (!who)
|
|
p = current;
|
|
else
|
|
p = find_task_by_vpid(who);
|
|
if (p)
|
|
ret = get_task_ioprio(p);
|
|
break;
|
|
case IOPRIO_WHO_PGRP:
|
|
if (!who)
|
|
pgrp = task_pgrp(current);
|
|
else
|
|
pgrp = find_vpid(who);
|
|
do_each_pid_thread(pgrp, PIDTYPE_PGID, p) {
|
|
tmpio = get_task_ioprio(p);
|
|
if (tmpio < 0)
|
|
continue;
|
|
if (ret == -ESRCH)
|
|
ret = tmpio;
|
|
else
|
|
ret = ioprio_best(ret, tmpio);
|
|
} while_each_pid_thread(pgrp, PIDTYPE_PGID, p);
|
|
break;
|
|
case IOPRIO_WHO_USER:
|
|
uid = make_kuid(current_user_ns(), who);
|
|
if (!who)
|
|
user = current_user();
|
|
else
|
|
user = find_user(uid);
|
|
|
|
if (!user)
|
|
break;
|
|
|
|
do_each_thread(g, p) {
|
|
if (!uid_eq(task_uid(p), user->uid) ||
|
|
!task_pid_vnr(p))
|
|
continue;
|
|
tmpio = get_task_ioprio(p);
|
|
if (tmpio < 0)
|
|
continue;
|
|
if (ret == -ESRCH)
|
|
ret = tmpio;
|
|
else
|
|
ret = ioprio_best(ret, tmpio);
|
|
} while_each_thread(g, p);
|
|
|
|
if (who)
|
|
free_uid(user);
|
|
break;
|
|
default:
|
|
ret = -EINVAL;
|
|
}
|
|
|
|
rcu_read_unlock();
|
|
return ret;
|
|
}
|