CVE-2026-89865 in Linux
Summary
by MITRE • 09/17/2026
In the Linux kernel, the following vulnerability has been resolved:
scsi: qla2xxx: Zero SFP DMA buffer in FRU/I2C bsg handlers
The FRU and I2C bsg handlers stage their transfer in a DMA_POOL_SIZE (256-byte) bounce buffer obtained from dma_pool_alloc(), which does not zero the allocation. They initialize only a few leading bytes before handing the buffer to qla2x00_write_sfp().
qla2x00_write_sfp() can override the transfer length with a user-supplied value:
if (len == 1) opt |= BIT_0; if (opt & BIT_0) len = *sfp;
*sfp is the first byte of the (user-controlled) payload, so len can grow up to 255. The device then DMA-reads len bytes from the 256-byte pool buffer. Since only a small prefix was written (e.g. MAX_FRU_SIZE == 36 bytes for a FRU version, one byte for a FRU status register), the hardware reads past the initialized region and writes up to ~219 bytes of stale DMA-pool heap memory to the device flash.
Allocate the buffer with dma_pool_zalloc() in all five FRU/I2C handlers so any bytes beyond the initialized data are zero rather than stale heap contents.
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Analysis
by VulDB Data Team • 09/17/2026
The Linux kernel driver for QLogic Fibre Channel adapters, specifically qla2xxx, contains a critical information disclosure vulnerability within its firmware read and update (FRU) and Inter-Integrated Circuit (I2C) block device interface handlers. This flaw stems from improper memory management practices when staging data transfers to the hardware via Direct Memory Access. The affected code paths utilize dma_pool_alloc() to obtain a 256-byte bounce buffer for communication with the SFP module or I2C devices. Unlike standard zeroing allocation functions, dma_pool_alloc does not guarantee that the returned memory is cleared of previous contents. Consequently, any data previously stored in this pool region remains present unless explicitly overwritten by the driver logic.
The technical severity of this vulnerability is exacerbated by a specific logic error within the qla2x00_write_sfp function, which processes these buffers before transmission to the hardware. The handler initializes only a small prefix of the buffer with relevant command data, such as thirty-six bytes for FRU version queries or single bytes for status registers. However, the driver allows user-supplied input from the block device interface to override the transfer length parameter under certain conditions. Specifically, if the initial length is one and specific options are set, the code reads the first byte of the payload to determine a new, potentially much larger length value that can reach up to 255 bytes. This mechanism effectively trusts user input to define how much data should be transmitted without verifying that the entire range has been properly initialized by the driver.
As a result of this unchecked length extension combined with the uninitialized memory state, the hardware performs a DMA read operation spanning far beyond the small region explicitly written by the kernel code. The adapter reads approximately two hundred and nineteen bytes of stale heap data from the dma_pool buffer that were not intended for transmission to the device flash or I2C bus. This behavior constitutes an out-of-bounds read vulnerability where sensitive kernel memory contents are exposed through hardware operations. An attacker with access to the bsg interface, which typically requires root privileges but may be accessible via container escapes or misconfigured permissions, can trigger these handlers to leak internal kernel state information into device registers or logs associated with the SFP module interaction.
From a classification perspective, this vulnerability aligns with CWE-120 Buffer Copy without Checking Size of Input and CWE-787 Out-of-bounds Write in some interpretations depending on how the data is consumed downstream, but more accurately reflects CWE-200 Information Exposure through an Error Message or Unintended Data Leakage. In terms of the MITRE ATT&CK framework for Linux systems, this behavior maps to T1059 Command and Scripting Interpreter if leveraged via bsg tools, and specifically relates to data exfiltration techniques where internal system state is revealed through peripheral device interactions. The lack of memory sanitization prior to DMA operations represents a fundamental failure in secure coding practices regarding buffer lifecycle management.
To mitigate this vulnerability, the primary remediation involves modifying the allocation strategy for the bounce buffers used in all five FRU and I2C bsg handlers within the qla2xxx driver. Developers must replace calls to dma_pool_alloc with dma_pool_zalloc. This function ensures that every byte of the allocated 256-byte buffer is explicitly zeroed before use, thereby eliminating any possibility of stale heap data being transmitted during DMA operations regardless of how the transfer length is manipulated by user input. Additionally, implementing strict bounds checking on the len variable relative to the actual initialized payload size would provide defense-in-depth against similar logic errors in future code modifications. System administrators should ensure that access to bsg devices is restricted to trusted processes and consider applying kernel patches as soon as they become available for supported distributions.