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4987a5763f
This change should cause no difference in behavior; it just cleans up some hazardous code that could have become a problem in the future. MSG_NO_SHARED_FRAGS is a kernel-internal flag that cancels the effect of MSG_SPLICE_PAGES, another kernel-internal flag that influences the data-sharing semantics of SKBs. Prevent passing this flag in from userspace via sendmsg() by adding it to MSG_INTERNAL_SENDMSG_FLAGS. This is not currently an observable problem because MSG_NO_SHARED_FRAGS only has an effect if kernel code adds MSG_SPLICE_PAGES to it. The only codepath that adds MSG_SPLICE_PAGES to user-supplied flags from which MSG_NO_SHARED_FRAGS hasn't been cleared is the path tcp_bpf_sendmsg -> tcp_bpf_send_verdict -> tcp_bpf_push, and that is not a problem because tcp_bpf_sendmsg always intentionally sets MSG_NO_SHARED_FRAGS anyway. Signed-off-by: Jann Horn <jannh@google.com> Link: https://patch.msgid.link/20260512-msg_no_shared_frags-v1-1-55ea46760331@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>