EUVD-2025-209675
GHSA-7g25-3chf-ppwr
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
4DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
net: qrtr: Drop the MHI auto_queue feature for IPCR DL channels
MHI stack offers the 'auto_queue' feature, which allows the MHI stack to auto queue the buffers for the RX path (DL channel). Though this feature simplifies the client driver design, it introduces race between the client drivers and the MHI stack. For instance, with auto_queue, the 'dl_callback' for the DL channel may get called before the client driver is fully probed. This means, by the time the dl_callback gets called, the client driver's structures might not be initialized, leading to NULL ptr dereference.
Currently, the drivers have to workaround this issue by initializing the internal structures before calling mhi_prepare_for_transfer_autoqueue(). But even so, there is a chance that the client driver's internal code path may call the MHI queue APIs before mhi_prepare_for_transfer_autoqueue() is called, leading to similar NULL ptr dereference. This issue has been reported on the Qcom X1E80100 CRD machines affecting boot.
So to properly fix all these races, drop the MHI 'auto_queue' feature altogether and let the client driver (QRTR) manage the RX buffers manually. In the QRTR driver, queue the RX buffers based on the ring length during probe and recycle the buffers in 'dl_callback' once they are consumed. This also warrants removing the setting of 'auto_queue' flag from controller drivers.
Currently, this 'auto_queue' feature is only enabled for IPCR DL channel. So only the QRTR client driver requires the modification.
AnalysisAI
Null pointer dereference in the Linux kernel QRTR (Qualcomm IPC Router) driver via MHI auto_queue feature causes denial of service on Qualcomm X1E80100 CRD machines during boot. The vulnerability occurs when the MHI stack invokes the DL (downlink) callback before the QRTR client driver is fully probed, accessing uninitialized driver structures. A local privileged attacker can trigger kernel panic by exploiting the race condition between MHI buffer auto-queuing and driver initialization, affecting systems relying on QRTR over MHI transport.
Technical ContextAI
The vulnerability exists in the QRTR driver's integration with the Modem Host Interface (MHI) stack, which is used for communication with Qualcomm modems. The MHI stack provides an 'auto_queue' feature that automatically queues receive buffers for downlink (DL) channels without requiring explicit management by the client driver. However, this feature introduces a critical race condition: the MHI stack may invoke the dl_callback handler before the QRTR driver completes its probe sequence, at which point internal data structures (rings, callbacks, buffers) are not yet initialized. This leads to CWE-476 (Null Pointer Dereference) when the callback attempts to access these uninitialized pointers. The fix removes the auto_queue mechanism entirely, requiring the QRTR driver to manually manage RX buffer lifecycle during probe and recycle consumed buffers in the dl_callback.
RemediationAI
Upgrade to patched Linux kernel versions: 6.18.17 or later for 6.18.x, 6.19.6 or later for 6.19.x, or 7.0 for 7.x branches. Apply commits 7bdff9b9b0c65ac7105416fe3a40686832515e20, 8c464e00e0754e016816b1860fa9592dcad80eb2, or 51731792a25cb312ca94cdccfa139eb46de1b2ef depending on kernel branch. For affected Qualcomm X1E80100 CRD devices or similar platforms using QRTR, prioritize kernel updates to resolve boot-time crashes. No workaround exists without the fix since the race condition is inherent to the auto_queue mechanism; devices must update kernel to restore stability. References: https://git.kernel.org/stable/c/7bdff9b9b0c65ac7105416fe3a40686832515e20
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