From: Xiang Mei (Microsoft) Date: Mon, 13 Jul 2026 23:32:30 +0000 (+0000) Subject: bpf: tcp: fix double sock release on batch realloc X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=980a813452754f8001704744e92f7aa697c53dd3;p=thirdparty%2Fkernel%2Flinux.git bpf: tcp: fix double sock release on batch realloc bpf_iter_tcp_batch() releases the current batch via bpf_iter_tcp_put_batch(), which drops the socket refs and rewrites each slot with the socket cookie, then grows the batch. cur_sk/end_sk are kept for bpf_iter_tcp_resume(), but on realloc failure the function returns ERR_PTR() before resume runs, leaving cur_sk < end_sk over slots that now hold cookies rather than sock pointers. bpf_iter_tcp_seq_stop() then calls bpf_iter_tcp_put_batch() again and dereferences a cookie as a struct sock. Empty the batch on the failure path so stop() does not release it again. The sockets were already freed by the first bpf_iter_tcp_put_batch(), so nothing leaks, and a later read() rescans the bucket from the start instead of skipping it. The sibling GFP_NOWAIT failure path still holds real socket references and is left for stop() to release. BUG: KASAN: null-ptr-deref in __sock_gen_cookie Read of size 8 at addr 0000000000000059 by task exploit ... __sock_gen_cookie (net/core/sock_diag.c:28) bpf_iter_tcp_put_batch (net/ipv4/tcp_ipv4.c:2918) bpf_iter_tcp_seq_stop (net/ipv4/tcp_ipv4.c:3270) bpf_seq_read (kernel/bpf/bpf_iter.c:205) vfs_read (fs/read_write.c:572) ksys_read (fs/read_write.c:716) do_syscall_64 entry_SYSCALL_64_after_hwframe Kernel panic - not syncing: Fatal exception Fixes: cdec67a489d4 ("bpf: tcp: Make sure iter->batch always contains a full bucket snapshot") Reported-by: AutonomousCodeSecurity@microsoft.com Signed-off-by: Xiang Mei (Microsoft) Reviewed-by: Eric Dumazet Reviewed-by: Jordan Rife Link: https://patch.msgid.link/20260713233230.3553593-1-xmei5@asu.edu Signed-off-by: Paolo Abeni --- diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index aada52769057..b8887cdd66c5 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -3146,8 +3146,11 @@ static struct sock *bpf_iter_tcp_batch(struct seq_file *seq) bpf_iter_tcp_put_batch(iter); err = bpf_iter_tcp_realloc_batch(iter, expected * 3 / 2, GFP_USER); - if (err) + if (err) { + iter->cur_sk = 0; + iter->end_sk = 0; return ERR_PTR(err); + } sk = bpf_iter_tcp_resume(seq); if (!sk)