CVE-2026-98851netfilter: nft_flow_offload: drop flowtable reference on init error path

Official description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_flow_offload: drop flowtable reference on init error path nft_flow_offload_init() bumps the flowtable use count with nft_use_inc() before calling nf_ct_netns_get(). When the latter fails, the error is returned as-is and the reference is leaked. The upper layers do not balance it either: nf_tables_newexpr() clears expr->ops when the expression init callback fails, so the nft_expr_more() iteration in nft_rule_expr_deactivate() and nf_tables_rule_destroy() stops right before the failed expression and its ->destroy callback, which would drop the reference, never runs. Each failed rule addition therefore leaks one flowtable reference and the flowtable can no longer be removed: NFT_MSG_DELFLOWTABLE keeps reporting -EBUSY even though no rule references it. Save the nf_ct_netns_get() return value and undo the nft_use_inc() when it fails, restoring the inc/dec pairing within nft_flow_offload_init() itself.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4e5a6d89083af6f23f0ac2cb611ef267590a3ece
• https://git.kernel.org/stable/c/1f43b6b099fa39032780b9494cedfd98f318f3c4
• https://git.kernel.org/stable/c/87f4914758f2da10b56cdb7f90ed815ade1e8ea3
• https://git.kernel.org/stable/c/1d27214fd9a4d2c0c6d998fc9d4fb61448a3438e
• https://git.kernel.org/stable/c/64ac0cb574c740bf723affb79b646eeba920db6b
• https://git.kernel.org/stable/c/c5f91098edee98c015f78488460a0609e62582a5
• https://git.kernel.org/stable/c/4cd378423a33194a773c267fc58606d28fce95cf
• https://git.kernel.org/stable/c/747928b5d4ff8c8de55138a54c13980e4bb88578