bpf, sockmap: Fix self-redirect copied_seq double-counting

Overview

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

bpf, sockmap: Fix self-redirect copied_seq double-counting

When a BPF stream_verdict program redirects an skb back to the same socket (self-redirect with BPF_F_INGRESS), sk_psock_verdict_apply() calls tcp_eat_skb() which advances tcp_sk->copied_seq. However, the skb is then delivered to the socket's psock ingress queue and later read by tcp_bpf_recvmsg_parser(), which also advances copied_seq via the copied_from_self accounting path. This double-counting causes copied_seq to advance by 2x the actual data length, triggering:

TCP recvmsg seq # bug 2: copied BF2E806, seq BF2E7FD,
rcvnxt BF2E806, fl 0 WARNING: net/ipv4/tcp.c:2745 at tcp_recvmsg_locked+0x72b/0x2640 Call Trace: tcp_recvmsg+0x10a/0x500 sock_recvmsg+0x168/0x1d0 __sys_recvfrom+0x19a/0x2a0 __x64_sys_recvfrom+0xe4/0x1f0 do_syscall_64+0xf7/0x530 entry_SYSCALL_64_after_hwframe+0x77/0x7f

cleanup rbuf bug: copied BF2E806 seq BF2E806 rcvnxt BF2E806 WARNING: net/ipv4/tcp.c:1609 at tcp_cleanup_rbuf+0xf2/0x1c0 Call Trace: tcp_recvmsg_locked+0x8d1/0x2640 tcp_recvmsg+0x10a/0x500 sock_recvmsg+0x168/0x1d0 __sys_recvfrom+0x19a/0x2a0 __x64_sys_recvfrom+0xe4/0x1f0 do_syscall_64+0xf7/0x530 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Fix this by converting self-redirect verdict to __SK_PASS at the beginning of sk_psock_verdict_apply(). This bypasses the __SK_REDIRECT case entirely (which calls sk_psock_eat_skb), letting the __SK_PASS path queue the skb to the psock ingress queue. The data is then read via tcp_bpf_recvmsg_parser(), which advances copied_seq exactly once through copied_from_self. Cross-socket redirects continue through __SK_REDIRECT with sk_psock_eat_skb() unchanged.

Affected

• Linux >= fe735073a50eaa71aceb2e990827fe26f33cddd6 < cf9aefb26a071cb8b6fdd761c27e022a1184946d
• Linux >= e5c6de5fa025882babf89cecbed80acf49b987fa < dc98def81e3c629e25fcdd5753b1db93aab27ce9
• Linux >= e5c6de5fa025882babf89cecbed80acf49b987fa < ef6f2182fee6b9721c005ccfc6aec0a47f79bbfa
• Linux >= e5c6de5fa025882babf89cecbed80acf49b987fa < ae1ffd04e98beefbe5d83335d506b0bcd5c2a6b3
• Linux >= e5c6de5fa025882babf89cecbed80acf49b987fa < 88942054191185c6f8bea5568cbb5614d1e99af9
• Linux >= e5c6de5fa025882babf89cecbed80acf49b987fa < 490a83d6386eec1d29f470c8d7331677fb46c3b7
• Linux f9b4a0b537be7a6e5f002ca64b09dcca9c14e6ed
• Linux >= 6.1.32 < 6.1.189
• Linux >= 6.3.6 < 6.4
• Linux 6.4

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.