net/smc: fix use-after-free in smc_rx_pipe_buf_release()

In the Linux kernel, the following vulnerability has been resolved: net/smc: fix use-after-free in smc_rx_pipe_buf_release() smc_rx_splice() hands RMB pages to a pipe and takes a socket reference per entry so the smc_sock stays alive until the reader finishes. The connection does not: a concurrent close runs smc_conn_free(), which releases the receive buffer back to the link group pool. smc_rx_pipe_buf_release() tests sk_state before taking the socket lock. The state can change between the test and the lock, and smc_rx_update_cons() then dereferences conn->rmb_desc and walks conn->lgr, which smc_conn_free() has already released. On the is_reg_err path smcr_buf_unuse() frees the descriptor outright, so this is a use-after-free. Take the socket lock first and test conn->freed instead. smc_conn_free() sets that flag before releasing anything, and every caller holds the socket lock. The two paths exclude each other: either the pipe release runs first with everything valid, or it sees the flag and skips the update.

Source published

11 Sep 2026 19:42:42 UTC

Source modified

19 Oct 2026 08:46:06 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 3.1 · 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H