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If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you! ** Tags added: verification-needed-trusty ** Tags added: verification-needed-vivid -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1527643 Title: use after free of task_struct->numa_faults in task_numa_find_cpu Status in linux package in Ubuntu: Fix Released Status in linux source package in Trusty: Fix Committed Status in linux source package in Vivid: Fix Committed Status in linux source package in Wily: Fix Committed Status in linux source package in Xenial: Fix Released Bug description: [Impact] The use-after-free invalid read bug, which happens in really tricky case, would use the numa_faults data already freed for the NUMA balance to make a decision to migrate the exiting process. The bug was found by the Ubuntu-3.13.0-65 with KASan backported. binary package: http://kernel.ubuntu.com/~gavinguo/kasan/Ubuntu-3.13.0-65.105/ source code: http://kernel.ubuntu.com/git/gavinguo/ubuntu-trusty-amd64.git/log/?h=Ubuntu-3.13.0-65-kasan ================================================================== BUG: KASan: use after free in task_numa_find_cpu+0x64c/0x890 at addr ffff880dd393ecd8 Read of size 8 by task qemu-system-x86/3998900 ============================================================================= BUG kmalloc-128 (Tainted: G B ): kasan: bad access detected ----------------------------------------------------------------------------- INFO: Allocated in task_numa_fault+0xc1b/0xed0 age=41980 cpu=18 pid=3998890 __slab_alloc+0x4f8/0x560 __kmalloc+0x1eb/0x280 task_numa_fault+0xc1b/0xed0 do_numa_page+0x192/0x200 handle_mm_fault+0x808/0x1160 __do_page_fault+0x218/0x750 do_page_fault+0x1a/0x70 page_fault+0x28/0x30 SyS_poll+0x66/0x1a0 system_call_fastpath+0x1a/0x1f INFO: Freed in task_numa_free+0x1d2/0x200 age=62 cpu=18 pid=0 __slab_free+0x2ab/0x3f0 kfree+0x161/0x170 task_numa_free+0x1d2/0x200 finish_task_switch+0x1d2/0x210 __schedule+0x5d4/0xc60 schedule_preempt_disabled+0x40/0xc0 cpu_startup_entry+0x2da/0x340 start_secondary+0x28f/0x360 INFO: Slab 0xffffea00374e4f00 objects=37 used=17 fp=0xffff880dd393ecb0 flags=0x6ffff0000004080 INFO: Object 0xffff880dd393ecb0 @offset=11440 fp=0xffff880dd393f700 Bytes b4 ffff880dd393eca0: 0c 00 00 00 18 00 00 00 af 63 3a 04 01 00 00 00 .........c:..... Object ffff880dd393ecb0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff880dd393ecc0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff880dd393ecd0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff880dd393ece0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff880dd393ecf0: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff880dd393ed00: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff880dd393ed10: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk Object ffff880dd393ed20: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 kkkkkkkkkkkkkkk. CPU: 61 PID: 3998900 Comm: qemu-system-x86 Tainted: G B 3.13.0-65-generic #105 Hardware name: Supermicro X8QB6/X8QB6, BIOS 2.0c 06/11/2 ffffea00374e4f00 ffff8816c572b420 ffffffff81a6ce35 ffff88045f00f500 ffff8816c572b450 ffffffff81244aed ffff88045f00f500 ffffea00374e4f00 ffff880dd393ecb0 0000000000000012 ffff8816c572b478 ffffffff8124ac36 Call Trace: [<ffffffff81a6ce35>] dump_stack+0x45/0x56 [<ffffffff81244aed>] print_trailer+0xfd/0x170 [<ffffffff8124ac36>] object_err+0x36/0x40 [<ffffffff8124cbf9>] kasan_report_error+0x1e9/0x3a0 [<ffffffff8124d260>] kasan_report+0x40/0x50 [<ffffffff810dda7c>] ? task_numa_find_cpu+0x64c/0x890 [<ffffffff8124bee9>] __asan_load8+0x69/0xa0 [<ffffffff814f5c38>] ? find_next_bit+0xd8/0x120 [<ffffffff810dda7c>] task_numa_find_cpu+0x64c/0x890 [<ffffffff810de16c>] task_numa_migrate+0x4ac/0x7b0 [<ffffffff810de523>] numa_migrate_preferred+0xb3/0xc0 [<ffffffff810e0b88>] task_numa_fault+0xb88/0xed0 [<ffffffff8120ef02>] do_numa_page+0x192/0x200 [<ffffffff81211038>] handle_mm_fault+0x808/0x1160 [<ffffffff810d7dbd>] ? sched_clock_cpu+0x10d/0x160 [<ffffffff81068c52>] ? native_load_tls+0x82/0xa0 [<ffffffff81a7bd68>] __do_page_fault+0x218/0x750 [<ffffffff810c2186>] ? hrtimer_try_to_cancel+0x76/0x160 [<ffffffff81a6f5e7>] ? schedule_hrtimeout_range_clock.part.24+0xf7/0x1c0 [<ffffffff81a7c2ba>] do_page_fault+0x1a/0x70 [<ffffffff81a772e8>] page_fault+0x28/0x30 [<ffffffff8128cbd4>] ? do_sys_poll+0x1c4/0x6d0 [<ffffffff810e64f6>] ? enqueue_task_fair+0x4b6/0xaa0 [<ffffffff810233c9>] ? sched_clock+0x9/0x10 [<ffffffff810cf70a>] ? resched_task+0x7a/0xc0 [<ffffffff810d0663>] ? check_preempt_curr+0xb3/0x130 [<ffffffff8128b5c0>] ? poll_select_copy_remaining+0x170/0x170 [<ffffffff810d3bc0>] ? wake_up_state+0x10/0x20 [<ffffffff8112a28f>] ? drop_futex_key_refs.isra.14+0x1f/0x90 [<ffffffff8112d40e>] ? futex_requeue+0x3de/0xba0 [<ffffffff8112e49e>] ? do_futex+0xbe/0x8f0 [<ffffffff81022c89>] ? read_tsc+0x9/0x20 [<ffffffff8111bd9d>] ? ktime_get_ts+0x12d/0x170 [<ffffffff8108f699>] ? timespec_add_safe+0x59/0xe0 [<ffffffff8128d1f6>] SyS_poll+0x66/0x1a0 [<ffffffff81a830dd>] system_call_fastpath+0x1a/0x1f Memory state around the buggy address: ffff880dd393eb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff880dd393ec00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff880dd393ec80: fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb ^ ffff880dd393ed00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc ffff880dd393ed80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== --------------------------8<-------------------------- $ addr2line 0xffffffff810dda7c -e usr/lib/debug/boot/vmlinux-3.13.0-65-generic -f -i task_numa_compare /home/gavin/os/ubuntu-trusty-amd64/kernel/sched/fair.c:1084 task_numa_find_cpu /home/gavin/os/ubuntu-trusty-amd64/kernel/sched/fair.c:1170 1083 if (cur->numa_group == env->p->numa_group) { 1084 imp = taskimp + task_weight(cur, env->src_nid) - 1085 task_weight(cur, env->dst_nid); In short, this is the use-after-free bug happening on the task_struct->numa_faults which is freed by the task_numa_free called by the finish_task_switch when the process is exiting. While the numa balance mechanism is triggering the do_numa_page fault and need to read the task_struct->numa_faults to determine if the current exiting process is needed to migrate to the other CPU for better memory access performance because of shorter distance to access memory on the other node. [Fix] There are 3 patches(renamed to A, B, and C) related to the backport. However, not all distribution need all the patches as some are already in the newer version of kernel. A: 156654f491dd ("sched/numa: Move task_numa_free() to __put_task_struct()"): included in v3.15-rc1~180^2~5. Reason: The patch is included because the task_numa_free() should be called inside the __put_task_struct() since the Fix C is based on the get_task_struct() to avoid the task_numa_free() being called. B: 1effd9f19324 ("sched/numa: Fix unsafe get_task_struct() in task_numa_assign()"): included in v3.18-rc3~21^2~5. Reason: Add the checking of the PF_EXITING flag to ensure the task has not been freed. C: 1dff76b92f69 ("sched/numa: Fix use-after-free bug in the task_numa_compare"): included in v4.5-rc2~8^2~1. Reason: However, as the commit message in B said "rcu_read_lock() can't save us from the final put_task_struct() in finish_task_switch()" so that's the patch C solved. For v3.13 Trusty there are 3 patches needed: - A, B, and C. For v3.16 Utopic there are 2 patches needed: - B and C. For v3.19 Vivid/v4.2 Wily there is 1 patch needed: - C. <-- clean cherry-pick. [Test Case] Running the reproducer for about 4 weeks with the backported Trusty kernel cannot find the KASan error messages in the dmesg. Reproducer: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1527643/+attachment/4595998/+files/kernel_panic_test.sh To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1527643/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
