CVE-2026-74631net: smc: fix splice entry lifetime imbalance in smc_rx_splice

Official description

In the Linux kernel, the following vulnerability has been resolved: net: smc: fix splice entry lifetime imbalance in smc_rx_splice smc_rx_splice() passes pages to splice_to_pipe() before taking the references that cover the lifetime of each splice entry. In the VM-backed RMB path, splice_to_pipe() may drop unqueued entries through smc_rx_spd_release(), while queued entries are released later via the pipe buffer callback. The old post-splice accounting also derives the number of queued VM pages from an offset mutated while building the descriptor, and a multi-page splice pairs one sock_hold() with multiple sock_put() calls. Take the page and socket references for every candidate entry before splice_to_pipe(), and drop the matching private state, page reference, and socket reference from smc_rx_spd_release() for entries that never get queued. This fixes a refcount imbalance that can underflow page refcounts and trigger a use-after-free.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/7ddc7af2ae7fc5a0c0635b245c0824c8b76de5cb
• https://git.kernel.org/stable/c/07ad246529d136d5ef441d5ab4c305d132ff3090
• https://git.kernel.org/stable/c/c841789e456ec6751342fa800639ce8e82ff0e6b
• https://git.kernel.org/stable/c/af02c67ce654356c58db20a0bb2db33ace3b07a8
• https://git.kernel.org/stable/c/ca8342b5fc24c249fdb998468f6a168b457c67e5
• https://git.kernel.org/stable/c/0b7d54cedea5cb158e21925ae0c6c2f5c87ed2a0
• https://git.kernel.org/stable/c/4515c78f4d9fd577270f012efeb062ea58b3682d
• https://git.kernel.org/stable/c/5d9686af2976741bbd79b150d1c9e60b81e7f12e