Using GDB to find structure info

As usual  load elf file

$gdb vmlinux

We are going to inspect the address layout of structure platform_device,

struct platform_device {
        const char      *name;
        int             id;
        bool            id_auto;
        struct device   dev;
        u32             num_resources;
        struct resource *resource;

        const struct platform_device_id *id_entry;
        char *driver_override; /* Driver name to force a match */

        /* MFD cell pointer */
        struct mfd_cell *mfd_cell;

        /* arch specific additions */
        struct pdev_archdata    archdata;
};


(gdb) p &((struct platform_device *)0)->name
$2 = (const char **) 0x0
(gdb) p &((struct platform_device *)0)->id
$3 = (int *) 0x8
(gdb) p &((struct platform_device *)0)->id_auto
$4 = (bool *) 0xc
(gdb) p &((struct platform_device *)0)->dev
$5 = (struct device *) 0x10

Above output shows the offset of different variables in the structure.

Enabling core dump on Ubuntu

type command,

ulimit -c unlimited

Still not present, monitor the logs here,
/var/log/apport.log

Interpreting values in stack using crash utility

This post shows how to figure out the values in stack using crash utility.

Let me explain a scenario:
Speculation: Process named Binder_5 is in the runqueue holding cgroup_mutex and looping there infinitely.

Below is the do while code which I m suspecting,
File: kerne/cgroups.c
Function: cgroup_attach_task
kernel version:3.10.17

                                                                    Figure 1:

Backtrace of Binder_5 task is as follows,

                                                                      Figure 2:

So from the do while, task_cgroup_from_root is called and this process(binder_5) was preempted out. It was because of some other high priority task might have come.

To confirm that we are in this loop for ever, we need to check the if condition(marked in red box in figure 1). Lets take the objdump of vmlinux and see how to figure out the value of ent.cgrp and cgrp. Both will be stored in stack.

Figure 3 show the partial objdump of function cgroup_attach_task(corresponding c function is shown in figure 1). It is taken using the following command.
$ arm-none-linux-gnueabi-objdump -D vmlinux > vmlinux_objdump.txt

                                                                      Figure 3:

Now we need to find the value of r5 and r0. And if they are same, then my speculation of infinite loop is correct. Tough job ahead :-). Lets have fun.

Finding the value of r5:
If we are lucky the value of r5 will be pushed in to stack during entry of function task_cgroup_from_root.
Here is the objdump:

                                                                     Figure 4:

Yes it is pushed to the stack.
Now figure 5 explains below how to find out the value of r5.
The left part of the figure 5 is created by printing the frame of task binder_5 using crash tool.
The command used,
crash> bt -f 2077
whree 2077 is the pid of process binder_5

                                                                                     Figure :5

push    {r4, r5, fp, ip, lr, pc}

In above instruction, pc will be stored at highest address in stack, followed by lr. And so on.
This is because arm linux stack type is full descending.

So value of r5 = 0xed306c00.

Finding the value of r0:
Now from figure 3, r0 is also stored at fp - 84 th location(marked in red box). so if we look at that location we could get what was the value of r0 when task_cgroup_from_root returned last time.

So for this, we need to find the value of fp first. This will be stored in the frame of task_cgroup_from_root. Same way as our r5 was stored.

Below figure shows how we found the value of fp.
The left side of figure 6 show the backtrace with frames same as figure 5. This time I used the notepad++.

                                                                                     Figure :6

So value of r0 and r5 are same and the speculation of of infinite loop is proved.
This was a bug in the kernel 3.10 and is fixed later. commit

Thanks,
Arun

RB Tree parsing in crash utility

Requirement: see all the virual address allocated to a process.

This is just for the demo purpose of tree command. If you want to do this you can do using command
crash>vm -p

from the ps output,

we pick the process ".android.chrome" whose task_struct address is 0xe22f6200

crash> struct task_struct 0xe22f6200
----strip-------
 mm = 0xedab1500,
----strip-------

we got the value of mm.

 crash> struct mm_struct 0xe22f6200
 struct mm_struct {          
  mmap = 0x1,                
  mm_rb = {                  
    rb_node = 0xc2b00000    
  },                        
  mmap_cache = 0x2,          

Now to list all vm_area(vm_start and vm_end)
crash> tree -t rbtree -r mm_struct.mm_rb 0xedab1500 -o 16 -s vm_area_struct.vm_start,vm_end

the value passed to -o is calulate as follows,
 crash> struct vm_area_struct.vm_rb  
struct vm_area_struct {              
  [16] struct rb_node vm_rb;        
}  

Crash Utility: How to view user space back trace

Step 1) Download gcore extension from,

http://people.redhat.com/anderson/extensions.html

Step 2) To build the module from the top-level crash- directory, enter:
  $ tar xzf crash-gcore-command-1.2.2.tar.gz
  $ mv crash-gcore-command-1.2.2/* extensions
  $ make extensions

Step 3) Extend gcore command as follows from crash command prompt,

crash> extend /projects/mobcom_andrwks_ext8/users/arunks/crashutility/src/crash_utility/extensions/gcore.so

Step 4) Use gcore command to dump the user core dump file

            $gcore 1291

            Where 1291 is the pid of the process. This creates a file core.1291.init

Step 5) Use gdb to view the back trace. Pass elf and the core dump file to gdb as follows

            $ arm-none-linux-gnueabi-gdb /projects/mobcom_andrwks_ext8/users/arunks/bringup_eos2b/android/out/target/product/amethyst/obj/EXECUTABLES/init_intermediates/LINKED/init core.1291.init

Step 6) view back trace by bt command.

(gdb) bt

#0  umount2 () at bionic/libc/arch-arm/syscalls/umount2.S:10

#1  0x0000e0a0 in check_fs (blk_device=0x648b0 "/dev/block/platform/e6bd0000.mmcif/by-name/MODEMLOG", fs_type=0x64900 "ext4", target=0x648e8 "/mnt/modemlog") at system/core/fs_mgr/fs_mgr.c:512

#2  0x0000e7ea in fs_mgr_mount_all (fstab=0x645c0) at system/core/fs_mgr/fs_mgr.c:512

#3  0x0000873a in do_mount_all (nargs=Unhandled dwarf expression opcode 0xf3

) at bionic/libc/include/string.h:217

#4  0x0000992a in execute_one_command () at system/core/init/init.c:939

#5  0x00009e56 in main (argc=Unhandled dwarf expression opcode 0xf3

) at system/core/init/init.c:939

(gdb)

Bug in Undefined Instruction Handler ARM

Problem Statement:

Multimedia team reported random user space crash.
The issue was tough to reproduce. If you run monkey test on, say 7 devices for around 5-10 hours.
They also indicated about a pattern, that SP is shifted by 8bytes in tombstone.

Most of the time crash was reproduced while returning from a bionic libc function strtoimax().
When objdump of strotimax was investigated, found few instruction which may cause corruption.
Out of them the most important one was vpush {d8} and vpop {d8}. This is basically a floating point instruction.

To confirm that vpush and vpop is causing the issue, added a new function called strtoimax_debug in bionic libc. This was a dummy function which does noting, but check for any stack corruption. We added those suspected instruction here,
Like stmdb sp!, {r4, r5, r6, r7, r8, r9, sl, fp, lr}, vpush and vpos
and check for the expected SP, if not generate an intentional data abort doing an ldr r0 [0]

From the result of this experiment, confirmed that the issue is with vpop instruction.

Now did bit study on how vfp instruction are executed. By default vfp engine is turned off druing a context switch. When a process executes floating point instruction, a undefined exception will be generated.
exception handler enables the vfp engine and jump back to the same instruction which caused the exception.
code looks okey in that perspective.

Tracing __und_usr(arch/arm/kernel/entry-armv.S) revealed that control came out of exception handler without performing do_vfp which is necessary to handle any vfp instruction when the engine is off.
This gave an indication that there can be only one possibility(for deviating the path) and that is an exception has triggered while executing the path.

Looking at the code further, saw that und_user is reading the instruction which cause the undefined exception. And comment says that this can cause a fault. Now the question is why it can falut?. Onepossible option is the code page might have reclaimed by other core. A fixup handler is register in the exception table. This is not the normal exception table. Here what I m talking is about kernel's fixup exception table.
But the fixup handler was not proper. It was calling ret_from_execption which retrun back to the next instruction. The problem is present in latest kernel aswell, but this problem is very rarely hit.

Now the fix is to return to the same instruction which cause fault instead of next instruction.

Some Notes:

The NEON/VFP register file is managed using lazy preserve (on UP systems) and
lazy restore (on both SMP and UP systems). This means that the register file is
kept 'live', and is only preserved and restored when multiple tasks are
contending for the NEON/VFP unit (or, in the SMP case, when a task migrates to
another core). Lazy restore is implemented by disabling the NEON/VFP unit after
every context switch, resulting in a trap when subsequently a NEON/VFP
instruction is issued, allowing the kernel to step in and perform the restore if
necessary.

Difference btw Neon and VFP
Neon donot support double precision
no complex operations like square root and divide.

Managed to push this fix upstream, [Link to kenrel.org]

Ram Dump - Linux System

Ram Dump
=========
Used for forensic analysis of a crashed or freeze kernel/system.
As the name points, its the dumping of complete ram contents for further investigation.

Divided into three sections
===================
The whole design is divided into three sections based on how ramdump is entered, transferred and stored.
1) Support in kernel to enter into ramdump mode when kernel crashes or freezes.
2) Support in boot-loader to detect ramdump, wait for a host tool to initiate ramdump and send the data to host.
3) A host tool which can receive data from device and save it on host PC file system.

Boot-loader Support
===============
During booting, boot-loader has to decide whether it has to enter in to ramdump mode or to boot linux normally. This is done by monitoring a magic value in any predefined location(typically SRAM register or any other, value should persists across reboot or reset). There are two magic numbers for example 0x12345678(for crash scenario) and  0x87654321(for freeze scenario). If the SRAM register is having any of the two magic number, the booloader will enter into ramdump mode and wait for the host side application to initiate upload. And if SRAM is not having any of these magic numbers, the bootloader will proceed with normal booting.

Kernel Support
===============
Kernel has to handle panic or freeze scenario and manage the magic numbers to be written in SRAM register.

Ramdump driver init
-----------------------
Write magic number for freeze scenario(MAGIC_FREEZE) in SRAM register.
Register for reboot and panic kernel notifiers.

During a freeze
-----------------
Kernel cannot do much here as the kernel is freezed. User has to press Power ON key for 10 sec, on which device will reset by PMU. While booting back,  boot-loader sees MAGIC_FREEZE in SRAM register(which was written during init) and enters to ramdump mode.

During a crash
------------------
Panic notifier registered from the ramdump driver will be called by kernel. Ramdump driver has to do few things.
a) Invoke cache sycn api to make sure all the content the ram is coherent.(flush_cache_all(),    outer_flush_all())
b) save core registers to ram
c) save MMU registers
d) write MAGIC_CRASH to SRAM regiter.
Then do a reboot. Now boot-loader finds the MAGIC_CRASH in SRAM register and goes to ramdump mode.

During a normal reboot
-------------------------
Device should not enter in to ramdump mode now.
Reboot notifier registered from the ramdump driver will be called by kernel. Ramdump driver clears MAGIC_FREEZE( written during the init ) and returns.

Saving pt_reg is done in two places,
File: arch/arm/mm/fault.c call the ramdump driver with pt_reg as argument to save for crashed cpu.
File: arch/arm/kernel/smp.c call ramdump driver with pt_reg from IPI_CPU_STOP to save the context of other cpus.

HOST side tool
============
Host side tool receive the data and saves to file system. We exploited fastboot to upload the data.

Design considerations
================
After a crash, device reboots and bootloader will be loaded again to RAM, which corrupts some part of the ram. This is something which cannot be avoided, unless ram upload is implemented in kernel itself. Another approach is to load the bootloader to a location which is of not much importance. For example, load bootloader to framebuffer location or some memory used by video subsystem or some carveout memory in the system.

U-boot relocates itself to the end of the ram. This behavior causes harm to the contents of the memory. So this should be taken care off.

Analyzing ramdump
==============
Ramdump can be analysed using T32 simulator or use amazing crash utility.
You need the corresponding vmlinux.

Debuggin Oops using Crash Utility

Crash log snippet of binder crash,

Before you start make sure the ramdump and vmlinux matches by using strings command,
strings vmlinux | grep "Linux version"

[49081.080352] Unable to handle kernel NULL pointer dereference at virtual address 00000030

[49081.088500] pgd = d748c000

[49081.091186] [00000030] *pgd=00000000

[49081.094787] Internal error: Oops: 5 [#1] PREEMPT SMP ARM

[49081.100067] kona_fb: die notifier invoked

[49081.104064] kona_display_crash_image:359 image_idx=4

[49081.109863] post_async:540 AXIPV has received the same buffer which is used

[49081.116790] post_async:541 It is likely that we see display tearing

[49081.123046] post_async:542 Preventing a potential lock-up by signalling

[49081.129669] Modules linked in: [last unloaded: bcmdhd_4330]

[49081.135253] CPU: 1    Tainted: G        W     (3.4.5+ #1)

[49081.140655] PC is at binder_get_node+0x8/0x34

[49081.144989] LR is at binder_thread_write+0x147c/0x239c

[49081.150115] pc : []    lr : []    psr: 20000053

[49081.150146] sp : f43a3e10  ip : f8f004fc  fp : 00000000

[49081.161560] r10: f8f004c4  r9 : 73622a85  r8 : 00000064

[49081.166778] r7 : f43a2000  r6 : f8f00460  r5 : 411e36f8  r4 : c0a69260

[49081.173278] r3 : 00000010  r2 : 411e3858  r1 : 411e36f8  r0 : f32c7a40

[49081.179779] Flags: nzCv  IRQs on  FIQs off  Mode SVC_32  ISA ARM  Segment user

[49081.186981] Control: 10c53c7d  Table: 9948c04a  DAC: 00000015

Disassemble of binder_get_node,

crash> dis binder_get_node

0xc03dc4a8 :   ldr     r3, [r0, #12]

0xc03dc4ac : b       0xc03dc4cc

0xc03dc4b0 : ldr     r2, [r3, #32]

0xc03dc4b4 :        sub     r0, r3, #16

0xc03dc4b8 :        cmp     r1, r2

0xc03dc4bc :        ldrcc   r3, [r3, #8]

0xc03dc4c0 :        bcc     0xc03dc4cc

0xc03dc4c4 :        bxls    lr

0xc03dc4c8 :        ldr     r3, [r3, #4]

0xc03dc4cc :        cmp     r3, #0

0xc03dc4d0 :        bne     0xc03dc4b0

0xc03dc4d4 :        mov     r0, r3

0xc03dc4d8 :        bx      lr

crash>

ldr  r3,[r0, #12]

From crash log above, r0 = f32c7a40

To confirm read memory 0xf32c7a40 + 0xc using  crash,

crash> rd f32c7a4c

f32c7a4c:  00008000                              ....

crash>

But r3 is 0x10. Which is not matching with 0x8000. So this means r0 has changed (since ldr  r3,[r0, #12]). Proves that crash not happened in first instance. It had looped for some time

C code binder_get_node,

static struct binder_node *binder_get_node(struct binder_proc *proc,

                                           void __user *ptr)

{

        struct rb_node *n = proc->nodes.rb_node;

        struct binder_node *node;

        while (n) {

                node = rb_entry(n, struct binder_node, rb_node);

                if (ptr < node->ptr)

                        n = n->rb_left;

                else if (ptr > node->ptr)

                        n = n->rb_right;

                else

                        return node;

        }

        return NULL;

}

Back trace from crash log,

[49081.971740] [] (binder_get_node+0x8/0x34) from [] (binder_thread_write+0x147c/0x239c)

[49081.981262] [] (binder_thread_write+0x147c/0x239c) from [] (binder_ioctl+0x37c/0x974)

[49081.990814] [] (binder_ioctl+0x37c/0x974) from [] (do_vfs_ioctl+0x4d8/0x54c)

[49081.999572] [] (do_vfs_ioctl+0x4d8/0x54c) from [] (sys_ioctl+0x34/0x54)

[49082.007904] [] (sys_ioctl+0x34/0x54) from [] (ret_fast_syscall+0x0/0x48)

Since the back trace was showing a sys_ioctl we iterated on stack to pick up the struct file * associated with.

Here is the hit,

crash> struct file f37cbef0

struct file {

  f_u = {

    fu_list = {

      next = 0xf37cb550,

      prev = 0xf2a0def0

    },

    fu_rcuhead = {

      next = 0xf37cb550,

      func = 0xf2a0def0

    }

 },

  f_path = {

    mnt = 0xf5015e58,

    dentry = 0xf3cc5d08

  },

  f_op = 0xc064dc0c,

----sniped---

  f_version = 0,

  private_data = 0xf2e9ca00,

  f_ep_links = {

    next = 0xf37cbf74,

    prev = 0xf37cbf74

  },

  f_tfile_llink = {

    next = 0xf37cbf7c,

    prev = 0xf37cbf7c

  },

  f_mapping = 0xf4090ad0

}

f_op symbol says it is binder_fops,

crash> sym 0xc064dc0c

c064dc0c (r) binder_fops

crash>

From code(drivers/staging/android/binder.c +3012) we figured out that private_data is binder_proc

crash> struct binder_proc 0xf2e9ca00

struct binder_proc {

  proc_node = {

    next = 0xf3514200,

    pprev = 0xc0a69c84

  },

  threads = {

    rb_node = 0xf2a10c84

  },

  nodes = {

    rb_node = 0xf2d1a7d0

  },

  refs_by_desc = {

    rb_node = 0xf3126284

  },

  refs_by_node = {

From the analysis of the code, we understand that crash happened while traversing the rb tree.

So tried to parse the rb tree using crash,

crash> tree -t rbtree -N 0xf2d1a7d0 -p

f2d1a7d0

  position: root

f2a00ad0

  position: root/l

f2a90e50

  position: root/r

f32c7a50

  position: root/r/r

10

  position: root/r/r/l

tree: invalid kernel virtual address: 18  type: "rb_node rb_left"

crash>

This shows that rb tress has a corrupted address to next left node.

0x10 which is the same value in r3 during crash.

And crash happened because of address 0x30.

[49081.080352] Unable to handle kernel NULL pointer dereference at virtual address 00000030

This explains why crashed.

0xc03dc4b0 : ldr     r2, [r3, #32]

R3 + #32 = 0x10 + 0x20 = 0x30

Dumping the corrupted struct rb_node from memory,

crash> struct rb_node f32c7a50

struct rb_node {

  rb_parent_color = 44100,

  rb_right = 0x2,

  rb_left = 0x10

}

crash>

This shows the rb tree is corrupted. Because rb_left and rb_right should have a valid kernel address or 0.

Dumping the memory from f32c7a00, 100 elements to inspect the memory,

crash> rd f32c7a00 100

f32c7a00:  f32c79fc 00000000 00000000 00000000   .y,.............

f32c7a10:  00000000 00000000 00000000 00000000   ................

f32c7a20:  00000000 00000000 00000000 00000000   ................

f32c7a30:  00000000 00000000 00000000 00000000   ................

f32c7a40:  01bb5e6b c03eed84 f4727600 00008000   k^....>..vr.....

f32c7a50:  0000ac44 00000002 00000010 f5c10000   D...............

f32c7a60:  00010000 b7c10000 00000000 00000000   ................

f32c7a70:  411e3858 411e3840 00001fe5 00000002   X8.A@8.A........

f32c7a80:  f32c7a7c 00000001 00000000 00000000   |z,.............

f32c7a90:  00000000 00000000 00000000 00000000   ................

f32c7aa0:  00000000 00000000 00000000 00000000   ................

f32c7ab0:  00000000 00000000 00000000 00000000   ................

f32c7ac0:  00000000 00000000 f32c7ac8 f32c7ac8   .........z,..z,.

f32c7ad0:  00000000 00000000 00000010 00000001   ................

f32c7ae0:  00000001 00000000 00000001 00000001   ................

f32c7af0:  00000000 00000000 00000000 f3faf330   ............0...

f32c7b00:  f3a6c000 00000000 00000000 00000000   ................

f32c7b10:  00000000 00000000 00000000 00000000   ................

f32c7b20:  00000000 00000000 00000000 00000000   ................

f32c7b30:  00000000 00000000 00000000 00000000   ................

f32c7b40:  006aefa7 f32c7b44 f32c7b44 00000003   ..j.D{,.D{,.....

f32c7b50:  f2bf1450 f3bef7d0 00000000 00000000   P...............

f32c7b60:  f3854bdc 00000001 00000000 00000000   .K..............

f32c7b70:  54d4c670 54d3f828 00001fe5 f32c7b7c   p..T(..T....|{,.

f32c7b80:  f32c7b7c 00000000 00000000 00000000   |{,.............

Dumping with symbols,

crash> rd -s f32c7a00 100

f32c7a00:  __crc_v4l2_norm_to_name+482177 00000000 00000000 00000000

f32c7a10:  00000000 00000000 00000000 00000000

f32c7a20:  00000000 00000000 00000000 00000000

f32c7a30:  00000000 00000000 00000000 00000000

f32c7a40:  01bb5e6b AUDIO_DRIVER_InterruptPeriodCB __crc_bmp18x_disable+1706299 00008000

f32c7a50:  0000ac44 00000002 00000010 __crc_generic_segment_checks+42732

f32c7a60:  00010000 b7c10000 00000000 00000000

f32c7a70:  411e3858 411e3840 00001fe5 00000002

f32c7a80:  __crc_v4l2_norm_to_name+482305 00000001 00000000 00000000

f32c7a90:  00000000 00000000 00000000 00000000

f32c7aa0:  00000000 00000000 00000000 00000000

f32c7ab0:  00000000 00000000 00000000 00000000

f32c7ac0:  00000000 00000000 __crc_v4l2_norm_to_name+482381 __crc_v4l2_norm_to_name+482381

f32c7ad0:  00000000 00000000 00000010 00000001

f32c7ae0:  00000001 00000000 00000001 00000001

f32c7af0:  00000000 00000000 00000000 __crc_qdisc_class_hash_grow+482810

f32c7b00:  __crc_rt_mutex_trylock+115850 00000000 00000000 00000000

f32c7b10:  00000000 00000000 00000000 00000000

f32c7b20:  00000000 00000000 00000000 00000000

f32c7b30:  00000000 00000000 00000000 00000000

f32c7b40:  006aefa7 __crc_v4l2_norm_to_name+482505 __crc_v4l2_norm_to_name+482505 00000003

f32c7b50:  __crc_usb_get_descriptor+260561 __crc_bdi_set_max_ratio+149137 00000000 00000000

f32c7b60:  __crc_snd_interval_ratnum+776842 00000001 00000000 00000000

f32c7b70:  54d4c670 54d3f828 00001fe5 __crc_v4l2_norm_to_name+482561

f32c7b80:  __crc_v4l2_norm_to_name+482561 00000000 00000000 00000000

Somebody has over written from f32c7a40

This causes rb_tree corruption.

Surprisingly there is an audio function address in the corrupted memory as highlighted above.

From the kernel logs we can see audio and rpc errors just before the crash.

Eg:

[48902.141143] WARNING: at /build/REL_sdb-common-android-jb-4.2.2_428843/android_hawaii_garnet_edn010/kernel/hawaii/3.4.5/sound/caph_hawaii/caph_pcm.c:248 PcmHwFree+0x8c/0xdc()

[48902.157012] ERROR timeout waiting for STOP REQ.t=30000 ret=0

[48902.162719] Modules linked in: [last unloaded: bcmdhd_4330]

[48902.168579] [] (unwind_backtrace+0x0/0x11c) from [] (warn_slowpath_common+0x4c/0x64)

[48902.178192] [] (warn_slowpath_common+0x4c/0x64) from [] (warn_slowpath_fmt+0x2c/0x3c)

[48902.187957] [] (warn_slowpath_fmt+0x2c/0x3c) from [] (PcmHwFree+0x8c/0xdc)

[48902.196716] [] (PcmHwFree+0x8c/0xdc) from [] (snd_pcm_release_substream+0x44/0xa4)

[48902.206512] [] (snd_pcm_release_substream+0x44/0xa4) from [] (snd_pcm_release+0x28/0x6c)

[48902.216735] [] (snd_pcm_release+0x28/0x6c) from [] (fput+0x10c/0x214)

[48902.224914] [] (fput+0x10c/0x214) from [] (filp_close+0x70/0x7c)

[48902.232879] [] (filp_close+0x70/0x7c) from [] (put_files_struct+0x90/0xec)

[48902.241668] [] (put_files_struct+0x90/0xec) from [] (do_exit+0x280/0x7e0)

[48902.250671] [] (do_exit+0x280/0x7e0) from [] (do_group_exit+0x88/0xb4)

[48902.259338] [] (do_group_exit+0x88/0xb4) from [] (get_signal_to_deliver+0x510/0x568)

[48902.269470] [] (get_signal_to_deliver+0x510/0x568) from [] (do_signal+0xc4/0x518)

[48902.278808] [] (do_signal+0xc4/0x518) from [] (do_notify_resume+0x18/0x50)

[48902.287567] [] (do_notify_resume+0x18/0x50) from [] (work_pending+0x24/0x28)

Conclusion is one possible suspect for corruption can be Audio.