CVE-2024-41042 Information

Description

In the Linux kernel the following vulnerability has been resolved:

netfilter: nf_tables: prefer nft_chain_validate

nft_chain_validate already performs loop detection because a cycle will result in a call stack overflow (ctx->level >= NFT_JUMP_STACK_SIZE).

It also follows maps via ->validate callback in nft_lookup so there appears no reason to iterate the maps again.

nf_tables_check_loops() and all its helper functions can be removed. This improves ruleset load time significantly from 23s down to 12s.

This also fixes a crash bug. Old loop detection code can result in unbounded recursion:

BUG: TASK stack guard page was hit at …. Oops: stack guard page: 0000 [1] PREEMPT SMP KASAN CPU: 4 PID: 1539 Comm: nft Not tainted 6.10.0-rc5+ 1 [..]

with a suitable ruleset during validation of register stores.

I can’t see any actual reason to attempt to check for this from nft_validate_register_store() at this point the transaction is still in progress so we don’t have a full picture of the rule graph.

For nf-next it might make sense to either remove it or make this depend on table->validate_state in case we could catch an error earlier (for improved error reporting to userspace).

Reference

https://git.kernel.org/stable/c/9df785aeb7dcc8efd1d4110bb27d26005298ebae https://git.kernel.org/stable/c/cff3bd012a9512ac5ed858d38e6ed65f6391008c