High [CVE-2026-72339] fix off-by-one in BD ring consumption on build_skb failure

In the Linux kernel, the following vulnerability has been resolved: qede: fix off-by-one in BD ring consumption on build_skb failure qede_rx_build_skb() and qede_tpa_rx_build_skb() do not check for a NULL return from qede_build_skb(). When it returns NULL under memory pressure, the functions still consume a BD from the ring before returning NULL.

The callers then recycle additional BDs, resulting in one extra BD being consumed (off-by-one). This desynchronizes the BD ring, which can corrupt DMA page reference counts and lead to SLUB freelist corruption.

Commit 4e910dbe3650 ("qede: confirm skb is allocated before using") added a NULL check inside qede_build_skb() to prevent a NULL pointer dereference, but did not address the missing NULL checks in the callers, making this off-by-one reachable.

Fix this by adding NULL checks for the return value of qede_build_skb() in both qede_rx_build_skb() and qede_tpa_rx_build_skb(), returning NULL immediately before any BD ring manipulation. A flaw was found in the Linux kernel's qede component, which handles network device operations.

Under specific memory pressure conditions, an error in how network buffer descriptors (BDs) are managed can lead to an off-by-one issue. This desynchronizes the BD ring, potentially corrupting memory and causing system instability or a denial of service.