Re: [EXT] Re: [PATCH v5] i3c: Fix read from unreadable memory at i3c_master_queue_ibi()

From: Mukesh Kumar Savaliya
Date: Wed Mar 26 2025 - 03:11:04 EST




On 3/26/2025 12:28 PM, Manjunatha Venkatesh wrote:


-----Original Message-----
From: Mukesh Kumar Savaliya <quic_msavaliy@xxxxxxxxxxx>
Sent: Wednesday, March 26, 2025 12:15 PM
To: Frank Li <frank.li@xxxxxxx>; Manjunatha Venkatesh
<manjunatha.venkatesh@xxxxxxx>
Cc: alexandre.belloni@xxxxxxxxxxx; arnd@xxxxxxxx;
gregkh@xxxxxxxxxxxxxxxxxxx; bbrezillon@xxxxxxxxxx; linux-
i3c@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
rvmanjumce@xxxxxxxxx; stable@xxxxxxxxxxxxxxx
Subject: [EXT] Re: [PATCH v5] i3c: Fix read from unreadable memory at
i3c_master_queue_ibi()

Caution: This is an external email. Please take care when clicking links or
opening attachments. When in doubt, report the message using the 'Report
this email' button


On 3/25/2025 8:13 PM, Frank Li wrote:
Subject should be

i3c: Add NULL pointer check in i3c_master_queue_ibi()

yes, Aligned.
On Tue, Mar 25, 2025 at 03:53:32PM +0530, Manjunatha Venkatesh wrote:
As part of I3C driver probing sequence for particular device
instance, While adding to queue it is trying to access ibi variable
of dev which is not yet initialized causing "Unable to handle kernel
read from unreadable memory" resulting in kernel panic.

Below is the sequence where this issue happened.
1. During boot up sequence IBI is received at host from the slave device
before requesting for IBI, Usually will request IBI by calling
i3c_device_request_ibi() during probe of slave driver.
2. Since master code trying to access IBI Variable for the particular
device instance before actually it initialized by slave driver,
due to this randomly accessing the address and causing kernel panic.
3. i3c_device_request_ibi() function invoked by the slave driver where
dev->ibi = ibi; assigned as part of function call
i3c_dev_request_ibi_locked().
4. But when IBI request sent by slave device, master code trying to access
this variable before its initialized due to this race condition
situation kernel panic happened.

How about commit message as:

The I3C master driver may receive an IBI from a target device that has
not been probed yet. In such cases, the master calls
`i3c_master_queue_ibi()` to queue an IBI work task, leading to "Unable
to handle kernel read from unreadable memory" and resulting in a kernel
panic.

Typical IBI handling flow:
1. The I3C master scans target devices and probes their respective drivers.
2. The target device driver calls `i3c_device_request_ibi()` to enable IBI
and assigns `dev->ibi = ibi`.
3. The I3C master receives an IBI from the target device and calls
`i3c_master_queue_ibi()` to queue the target device driver's IBI handler
task.

However, since target device events are asynchronous to the I3C probe
sequence, step 3 may occur before step 2, causing `dev->ibi` to be
`NULL`, leading to a kernel panic.

Add a NULL pointer check in `i3c_master_queue_ibi()` to prevent
accessing an uninitialized `dev->ibi`, ensuring stability.


Fixes: 3a379bbcea0af ("i3c: Add core I3C infrastructure")
Cc: stable@xxxxxxxxxxxxxxx
Link:
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flor
e.kernel.org%2Flkml%2FZ9gjGYudiYyl3bSe%40lizhi-Precision-Tower-
5810%2

F&data=05%7C02%7Cmanjunatha.venkatesh%40nxp.com%7Ceda8be8c7abc4
3b4ab9

608dd6c31c8e7%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6387
856832

77582903%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYi
OiIwLjAu

MDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%
7C%7C

&sdata=oyc9Wv%2Fj8HMRFIiIGL9nIw0XvI6FsLK2SvsQJ55H7XI%3D&reserved=
0
Signed-off-by: Manjunatha Venkatesh <manjunatha.venkatesh@xxxxxxx>
---
Changes since v4:
- Fix added at generic places master.c which is applicable for all
platforms

drivers/i3c/master.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c index
d5dc4180afbc..c65006aa0684 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -2561,6 +2561,9 @@ static void
i3c_master_unregister_i3c_devs(struct i3c_master_controller *master)
*/
void i3c_master_queue_ibi(struct i3c_dev_desc *dev, struct i3c_ibi_slot
*slot)
{
+ if (!dev->ibi || !slot)
+ return;
+
1. Shouldn't this be a Logical AND ? what if slot is non NULL but the IBI is
NULL ?

[Manjunatha Venkatesh] : I think Logical OR operation is correct,
Since if any one of the variable is NULL need to return before accessing those variables.
I agree, i was incorrect.
2. This being void function, it doesn't say anything to caller if it's successful or
failed ? Should we make this non void function ?
if not, i am thinking it may run into multiple attempts, no log too.
[Manjunatha Venkatesh] : If required we can add error print log, Others please confirm your opinion on this.
atomic_inc(&dev->ibi->pending_ibis);
queue_work(dev->ibi->wq, &slot->work);
}
--
2.46.1