Re: Kernelnewbies Digest, Vol 168, Issue 5

Nov. 15, 2024

      Hi Sekhar,

I’ve fixed memory corruption issues in the past by replacing the memory cards. Have you tried swapping them out to see if the cards are the problem? Sometimes, even software stress tests won’t catch the issue. You might also want to test the setup on a different device using the same driver—that can help pinpoint the problem.

Hope this helps!
Dudley

On November 16, 2024 2:00:01 AM GMT+09:00, kernelnewbies-request@kernelnewbies.org wrote:
...
Send Kernelnewbies mailing list submissions to
  kernelnewbies@kernelnewbies.org
To subscribe or unsubscribe via the World Wide Web, visit
  https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
or, via email, send a message with subject or body 'help' to
  kernelnewbies-request@kernelnewbies.org
You can reach the person managing the list at
  kernelnewbies-owner@kernelnewbies.org
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Kernelnewbies digest..."
Today's Topics:
1. Help Needed: Debugging Memory Corruption results GPF (Muni Sekhar)
----------------------------------------------------------------------
Message: 1
Date: Fri, 15 Nov 2024 21:47:59 +0530
From: Muni Sekhar <munisekharrms@gmail.com>
To: kernel-hardening@lists.openwall.com,  kasan-dev
  <kasan-dev@googlegroups.com>, LKML <linux-kernel@vger.kernel.org>,
  kernelnewbies <kernelnewbies@kernelnewbies.org>
Subject: Help Needed: Debugging Memory Corruption results GPF
Message-ID:
  <CAHhAz+i+4iCn+Ddh1YvuMn1v-PfJj72m6DcjRaY+3vx7wLhFsQ@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Hi all,
I am encountering a memory corruption issue in the function
msm_set_laddr() from the Slimbus MSM Controller driver source code.
https://android.googlesource.com/kernel/msm/+/refs/heads/android-msm-sunfish...
In msm_set_laddr(), one of the arguments is ea (enumeration address),
which is a pointer to constant data. While testing, I observed strange
behavior:
The contents of the ea buffer get corrupted during a timeout scenario
in the call to:
timeout = wait_for_completion_timeout(&done, HZ);
Specifically, the ea buffer's contents differ before and after the
wait_for_completion_timeout() call, even though it's declared as a
pointer to constant data (const u8 *ea).
To debug this issue, I enabled KASAN, but it didn't reveal any memory
corruption. After the buffer corruption, random memory allocations in
other parts of the kernel occasionally result in a GPF crash.
Here is the relevant part of the code:
static int msm_set_laddr(struct slim_controller *ctrl, const u8 *ea,
                        u8 elen, u8 laddr)
{
   struct msm_slim_ctrl *dev = slim_get_ctrldata(ctrl);
   struct completion done;
   int timeout, ret, retries = 0;
   u32 *buf;
retry_laddr:
   init_completion(&done);
   mutex_lock(&dev->tx_lock);
   buf = msm_get_msg_buf(dev, 9, &done);
   if (buf == NULL)
       return -ENOMEM;
   buf[0] = SLIM_MSG_ASM_FIRST_WORD(9, SLIM_MSG_MT_CORE,
                                    SLIM_MSG_MC_ASSIGN_LOGICAL_ADDRESS,
                                    SLIM_MSG_DEST_LOGICALADDR,
                                    ea[5] | ea[4] << 8);
   buf[1] = ea[3] | (ea[2] << 8) | (ea[1] << 16) | (ea[0] << 24);
   buf[2] = laddr;
   ret = msm_send_msg_buf(dev, buf, 9, MGR_TX_MSG);
   timeout = wait_for_completion_timeout(&done, HZ);
   if (!timeout)
       dev->err = -ETIMEDOUT;
   if (dev->err) {
       ret = dev->err;
       dev->err = 0;
   }
   mutex_unlock(&dev->tx_lock);
   if (ret) {
       pr_err("set LADDR:0x%x failed:ret:%d, retrying", laddr, ret);
       if (retries < INIT_MX_RETRIES) {
           msm_slim_wait_retry(dev);
           retries++;
           goto retry_laddr;
       } else {
           pr_err("set LADDR failed after retrying:ret:%d", ret);
       }
   }
   return ret;
}
What I've Tried:
KASAN: Enabled it but couldn't identify the source of the corruption.
Debugging Logs: Added logs to print the ea contents before and after
the wait_for_completion_timeout() call. The logs show a mismatch in
the data.
Question:
How can I efficiently trace the source of the memory corruption in
this scenario?
Could wait_for_completion_timeout() or a related function cause
unintended side effects?
Are there additional tools or techniques (e.g., dynamic debugging or
specific kernel config options) that can help identify this
corruption?
Any insights or suggestions would be greatly appreciated!
-- 
Thanks,
Sekhar
------------------------------
Subject: Digest Footer
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
------------------------------
End of Kernelnewbies Digest, Vol 168, Issue 5
*********************************************

Dudley

tags

participants (1)