bpf: Fix out-of-bounds read of rtt_min in sock_ops

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix out-of-bounds read of rtt_min in sock_ops A sockops prog reading skops->rtt_min never checks the sk type: on the tcp_conn_request() path sock_ops->sk is a request_sock (non-full), and the ctx rewrite casts it to a tcp_sock (full) and reads rtt_min past the end of the request_sock, returning dirty adjacent memory. SEC("sockops") int prog(struct bpf_sock_ops *skops) { switch (skops->op) { case BPF_SOCK_OPS_RWND_INIT: leak = skops->rtt_min; /* reads the request_sock OOB */ ... } } For instance one such read returned rtt_min=0xffff8881, the high half of a leaked kernel pointer. Guarding that cast is exactly what SOCK_OPS_GET_FIELD() does -- it checks is_locked_tcp_sock and returns 0 when sock_ops->sk is not a locked full socket. Every other tcp_sock field in sock_ops goes through it; rtt_min is the only one open-coded, so it skips the check. Read rtt_min through SOCK_OPS_GET_FIELD() too. rtt_min is a bit special: it is a struct minmax and we only want the current min, so pass rtt_min.s[0].v. That is equivalent to the old hand-computed offset offsetof(struct tcp_sock, rtt_min) + sizeof_field(struct minmax_sample, t) (s[0] sits at rtt_min + 0 and .v at + sizeof(.t), i.e. what minmax_get() returns), so the loaded field is unchanged and only the full-sock guard is added. The two BUILD_BUG_ON()s that protected the hand-computed offset are no longer needed. Before patch: 0: r1 = (u64 )(r1 +0) ; r1 = skops->sk 1: r1 = (u32 )(r1 +2324) ; ((tcp_sock *)sk)->rtt_min.s[0].v After patch: 0: (u64 )(r1 +56) = r9 1: r9 = (u8 )(r1 +50) ; is_locked_tcp_sock 2: if r9 == 0 goto pc+4 ; not a locked full sock -> 0 3: r9 = (u64 )(r1 +56) 4: r1 = (u64 )(r1 +0) ; r1 = skops->sk 5: r1 = (u32 )(r1 +2324) ; rtt_min.s[0].v 6: goto pc+2 7: r9 = (u64 )(r1 +56) 8: r1 = 0

Timeline

1. Oct 18, 2026, 3:20 PM UTCCVE published
2. Oct 19, 2026, 9:23 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 44f0e43037d3a17b043843ba67610ac7c7e37db6 · fixed in 0c796efa919f52f788c22c79d1f1b70321696b3d; From 44f0e43037d3a17b043843ba67610ac7c7e37db6 · fixed in fc9d0e6e9d86fbefe7b8fe6ee49f4cf102add79d; From 44f0e43037d3a17b043843ba67610ac7c7e37db6 · fixed in fd6bf2721933d8c90bc4ce57f3e204c9295e7e3f; From 44f0e43037d3a17b043843ba67610ac7c7e37db6 · fixed in a8a9becbac93a9f54f4d565f1f3005eb08a7912f; From 44f0e43037d3a17b043843ba67610ac7c7e37db6 · fixed in 3a46f14e6cf375f3ca38f8f6e6524749e24ea0a8; From 44f0e43037d3a17b043843ba67610ac7c7e37db6 · fixed in 6785313d4fac96afb21ef193610c1fa88b1a9e64; From 44f0e43037d3a17b043843ba67610ac7c7e37db6 · fixed in cba54d142c43ec96d8c4d566f66439e8c0afded7; From 44f0e43037d3a17b043843ba67610ac7c7e37db6 · fixed in 75f8cf22463d82bb1fb0239a3d485fc8f4c8ef03

• Linux Linux

  4.16

• KernelLinux

  From 4.16.0 · fixed in 5.10.271; From 5.11.0 · fixed in 5.15.222; From 5.16.0 · fixed in 6.1.189; From 6.2.0 · fixed in 6.6.158; From 6.7.0 · fixed in 6.12.112; From 6.13.0 · fixed in 6.18.55; From 6.19.0 · fixed in 7.2.9

References 8