CVE-2026-72072net/mlx5e: macsec: fix use-after-free of metadata_dst on RX SC delete

Official description

In the Linux kernel, the following vulnerability has been resolved: net/mlx5e: macsec: fix use-after-free of metadata_dst on RX SC delete When an offloaded MACsec RX SC is deleted, macsec_del_rxsc_ctx() freed the per-SC metadata_dst with metadata_dst_free(), which kfree()s the object unconditionally and ignores the dst reference count. The RX datapath in mlx5e_macsec_offload_handle_rx_skb() looks up the SC under rcu_read_lock() via xa_load(), takes a reference with dst_hold() and attaches the dst to the skb with skb_dst_set(). A reader that already obtained the rx_sc pointer can race with the delete path and operate on freed memory. Fix the owner side by dropping the reference with dst_release() instead of freeing unconditionally, and convert the RX datapath to dst_hold_safe() so a reader racing the SC delete cannot attach a dst whose last reference was just dropped; only attach it when a reference was actually taken. mlx5e_macsec_add_rxsc() also published sc_xarray_element via xa_alloc() before rx_sc->md_dst was allocated and initialised, so a datapath reader that looked the SC up by fs_id could observe rx_sc with md_dst still NULL or, on weakly-ordered architectures, a non-NULL md_dst pointer whose contents were not yet visible. NULL-check the xa_load() result and md_dst on the datapath, and reorder add_rxsc() so the xa_alloc() publish happens only after md_dst is fully initialised; the xarray RCU publish then pairs with the rcu_read_lock()/xa_load() in the datapath. Note: macsec_del_rxsc_ctx() also kfree()s rx_sc->sc_xarray_element without an RCU grace period while the same datapath reads it under rcu_read_lock(); that is a separate pre-existing issue left to a follow-up patch. Found by 0sec automated security-research tooling (https://0sec.ai).

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb
• https://git.kernel.org/stable/c/218cc15a4c907659ad4b0e68c535c61594311205
• https://git.kernel.org/stable/c/4a5073b7b30243658f58b2d2d35a823da7fd34d9
• https://git.kernel.org/stable/c/ed3cc4218070d6b98bf5fb456dccae424fd38c4f
• https://git.kernel.org/stable/c/088873af13590ebde10de2ade847f57a05ec61c6
• https://git.kernel.org/stable/c/de74d8fd10291763d97b218f09adcc7513c975e4