UBUNTU-CVE-2026-23438: Null Pointer Dereference
In the Linux kernel, the following vulnerability has been resolved: net: mvpp2: guard flow control update with globaltxfc in buffer switching mvpp2bmswitchbuffers() unconditionally calls mvpp2bmpoolupdateprivfc() when switching between per-cpu and shared buffer pool modes. This function programs CM3 flow control registers via mvpp2cm3read()/mvpp2cm3write(), which dereference priv->cm3base without any NULL check. When the CM3 SRAM resource is not present in the device tree (the third reg entry added by commit 60523583b07c ("dts: marvell: add CM3 SRAM memory to cp11x ethernet device tree")), priv->cm3base remains NULL and priv->globaltxfc is false. Any operation that triggers mvpp2bmswitchbuffers(), for example an MTU change that crosses the jumbo frame threshold, will crash: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Mem abort info: ESR = 0x0000000096000006 EC = 0x25: DABT (current EL), IL = 32 bits pc : readl+0x0/0x18 lr : mvpp2cm3read.isra.0+0x14/0x20 Call trace: readl+0x0/0x18 mvpp2bmpoolupdatefc+0x40/0x12c mvpp2bmpoolupdateprivfc+0x94/0xd8 mvpp2bmswitchbuffers.isra.0+0x80/0x1c0 mvpp2changemtu+0x140/0x380 devsetmtu+0x1c/0x38 devsetmtuext+0x78/0x118 devsetmtu+0x48/0xa8 devifsioc+0x21c/0x43c devioctl+0x2d8/0x42c sockioctl+0x314/0x378 Every other flow control call site in the driver already guards hardware access with either priv->globaltxfc or port->txfc. mvpp2bmswitchbuffers() is the only place that omits this check. Add the missing priv->globaltxfc guard to both the disable and re-enable calls in mvpp2bmswitchbuffers(), consistent with the rest of the driver.
Affected Software
Remediation
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ubuntu/linux-gcp-fipsto a version that resolves this vulnerability.Fixed in 6.8.0-1064.72+fips1 - Compensating control
Modify mvpp2_bm_switch_buffers() so both the flow-control disable and re-enable calls to mvpp2_bm_pool_update_priv_fc() are guarded by priv->global_tx_fc before accessing CM3 flow-control registers.