CVE-2026-68335

In the Linux kernel, the following vulnerability has been resolved:

rds: drop incoming messages that cross network namespace boundaries

rds_find_bound() looks up the destination socket using a global rhashtable keyed solely on (addr, port, scope_id). Network namespaces are not part of the key, so a sender in netns A can deliver an incoming message (inc) to a socket that lives in a different netns B.

When this happens, inc->i_conn points to an rds_connection whose c_net is netns A, but the receiving rs lives in netns B. Once the child process that created netns A exits, cleanup_net() calls rds_loop_exit_net() -> rds_loop_kill_conns() -> rds_conn_destroy(), freeing that connection. If the survivor socket in netns B still holds the inc, any subsequent dereference of inc->i_conn is a use-after-free.

There are two dangerous sites in rds_clear_recv_queue():

1. inc->i_conn->c_lcong (offset 88 of freed rds_connection, size 200) read via rds_recv_rcvbuf_delta() – confirmed by KASAN.
2. inc->i_conn->c_trans->inc_free(inc) (function pointer at offset 80) called via rds_inc_put() when the inc refcount reaches zero – same race window, potential call-through-freed-object primitive.

The bug is reachable from unprivileged user namespaces (CLONE_NEWUSER + CLONE_NEWNET), available since Linux 3.8.

Fix this by rejecting the delivery in rds_recv_incoming() when the socket returned by rds_find_bound() belongs to a different network namespace than the connection that carried the message. Use the existing rds_conn_net() / sock_net() helpers and net_eq() for the comparison.

Weakness

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory “belongs” to the code that operates on the new pointer.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/03c574112e5d066df0ddce36d7438e850bcf3050
• https://git.kernel.org/stable/c/0f8690e3869109cd5803ccb400889d20a0b54e0e
• https://git.kernel.org/stable/c/1e2e2d9806944fe485824d617c8b7c78116c22db
• https://git.kernel.org/stable/c/5521ae71e32a8069ed4ca6e792179dc57bc43ab2
• https://git.kernel.org/stable/c/742ff6f02545212e991cd8b45011e40d2c2ef25a
• https://git.kernel.org/stable/c/9591042533140dfe6608d9344806d567dcd39d02
• https://git.kernel.org/stable/c/abff41fd928328bbf3dda1140beb2e61fa424ccd
• https://git.kernel.org/stable/c/cfb3ce07b705e486e022a2f2b1242b48f13981ff