Multicast Join Vulnerability in Linux Kernel Affecting InfiniBand/IPoIB

CVE-2026-98347

What is CVE-2026-98347?

A race condition exists in the Linux kernel's InfiniBand subsystem related to multicast joining during interface flush operations. The ipoib_ib_dev_flush_light() function temporarily disables the multicast capability by clearing the IPOIB_FLAG_OPER_UP flag. However, a race occurs if the interface is brought down while the flush operation is ongoing, potentially restoring the flag after the device has been shut down. Consequently, this can cause the multicast work to hang indefinitely, leading to system deadlocks. To remedy this, a dedicated IPOIB_FLAG_MCAST_FLUSH flag has been introduced to manage multicast state without conflicting with device shutdown operations.

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