Public bug reported:
[Impact]
In function cpuacct_charge(), the NULL pointer dereference happens
with the stack pointer being zero inside the task_struct when the
task_cpu() is trying to access the member CPU of the struct
thread_info inside the stack. It's a use-after-free corruption
happening in the situation that the task_struct is released almost
concurrently before accessing the task_struct->stack.
void cpuacct_charge(struct task_struct *tsk, u64 cputime)
{
struct cpuacct *ca;
int cpu;
cpu = task_cpu(tsk);
rcu_read_lock();
ca = task_ca(tsk);
while (true) {
u64 *cpuusage = per_cpu_ptr(ca->cpuusage, cpu);
*cpuusage += cputime;
ca = parent_ca(ca);
if (!ca)
break;
}
rcu_read_unlock();
}
BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
IP: [<ffffffff810c3ff4>] cpuacct_charge+0x14/0x40
PGD 0
Oops: 0000 [#1] SMP
CPU: 10 PID: 148614 Comm: qemu-system-x86 Tainted: P W OE
4.4.0-45-generic #66~14.04.1-Ubuntu
Hardware name: Dell Inc. PowerEdge R630/02C2CP, BIOS 2.1.7 06/16/2016
task: ffff881ff0f01b80 ti: ffff88018fd70000 task.ti: ffff88018fd70000
RIP: 0010:[<ffffffff810c3ff4>] [<ffffffff810c3ff4>] cpuacct_charge+0x14/0x40
RSP: 0018:ffff88018fd73d10 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff8801931e8000 RCX: ffff88010caff200
RDX: ffff880124508000 RSI: 0066f757398831d6 RDI: ffff8801931e7fa0
RBP: ffff88018fd73d10 R08: ffffffffc04b8320 R09: 0000000000000001
R10: 0000000000000001 R11: 0000000000000000 R12: 0066f757398831d6
R13: 0066f757398b8997 R14: ffff8801931e7fa0 R15: 0000000000000001
FS: 00007f162aaf7700(0000) GS:ffff881ffe740000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000010 CR3: 000000011d86e000 CR4: 00000000003426e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Stack:
ffff88018fd73d28 ffffffff810b1a9f ffff8801931e8000 ffff88018fd73d40
ffffffffc069df72 ffff8801931e8000 ffff88018fd73da8 ffffffffc069f121
ffff881ff0f01b80 0000000000000000 ffff881ff0f01b80 ffffffff810bddc0
Call Trace:
[<ffffffff810b1a9f>] update_curr+0xdf/0x170
[<ffffffffc069df72>] kvm_vcpu_check_block+0x12/0x60 [kvm]
[<ffffffffc069f121>] kvm_vcpu_block+0x191/0x2d0 [kvm]
[<ffffffff810bddc0>] ? prepare_to_wait_event+0xf0/0xf0
[<ffffffffc06bb9ee>] kvm_arch_vcpu_ioctl_run+0x17e/0x3d0 [kvm]
[<ffffffffc06a1f8b>] kvm_vcpu_ioctl+0x2ab/0x640 [kvm]
[<ffffffff81174517>] ? perf_event_context_sched_in+0x87/0xa0
[<ffffffff81210d6d>] do_vfs_ioctl+0x2dd/0x4c0
[<ffffffff8111fa1f>] ? __audit_syscall_entry+0xaf/0x100
[<ffffffff81003176>] ? do_audit_syscall_entry+0x66/0x70
[<ffffffff81210fc9>] SyS_ioctl+0x79/0x90
[<ffffffff817fa4f6>] entry_SYSCALL_64_fastpath+0x16/0x75
Code: 9a 11 00 5b 48 c7 c0 f4 ff ff ff 5d eb df 66 0f 1f 84 00 00 00 00 00 0f
1f 44 00 00 55 48 8b 47 08 48 8b 97 78 07 00 00 48 89 e5 <48> 63 48 10 48 8b 52
60 48 8b 82 b8 00 00 00 48 03 04 cd c0 7a
RIP [<ffffffff810c3ff4>] cpuacct_charge+0x14/0x40
RSP <ffff88018fd73d10>
CR2: 0000000000000010
---[ end trace 419a30375d0e4622 ]---
[Fix]
The patch uses this_cpu_ptr() instead of getting the CPU number by
task_cpu() and proceeds to get the cpu_usage by per_cpu_ptr(). And
that can avoid accessing the thread_info inside the stack.
commit 73e6aafd9ea81498d31361f01db84a0118da2d1c
Author: Zhao Lei <zhao...@cn.fujitsu.com>
Date: Thu Mar 17 12:19:43 2016 +0800
sched/cpuacct: Simplify the cpuacct code
- Use for() instead of while() loop in some functions
to make the code simpler.
- Use this_cpu_ptr() instead of per_cpu_ptr() to make the code
cleaner and a bit faster.
Suggested-by: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Zhao Lei <zhao...@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Tejun Heo <hte...@gmail.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Link:
http://lkml.kernel.org/r/d8a7ef9592f55224630cb26dea239f05b6398a4e.1458187654.git.zhao...@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
[Test]
The test kernel has been tested by the Qemu and cannot be reproduced.
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Gavin Guo (mimi0213kimo)
Status: Incomplete
** Tags: sts xenial
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1775326
Title:
The kernel NULL pointer dereference happens when accessing the
task_struct by task_cpu() in function cpuacct_charge()
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1775326/+subscriptions
--
ubuntu-bugs mailing list
ubuntu-bugs@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
