cpumap: Zero-initialise xdp_rxq_info struct before running XDP program

When running an XDP program that is attached to a cpumap entry, we don't
initialise the xdp_rxq_info data structure being used in the xdp_buff
that backs the XDP program invocation. Tobias noticed that this leads to
random values being returned as the xdp_md->rx_queue_index value for XDP
programs running in a cpumap.

This means we're basically returning the contents of the uninitialised
memory, which is bad. Fix this by zero-initialising the rxq data
structure before running the XDP program.

Fixes: 9216477449f3 ("bpf: cpumap: Add the possibility to attach an eBPF program to cpumap")
Reported-by: Tobias Böhm <tobias@aibor.de>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20240305213132.11955-1-toke@redhat.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index 8a0bb80fe48a344964e4029fec5e895ee512babf..ef82ffc90cbe9d7aeab50c4856b45a52621a90a9 100644 (file)
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -178,7 +178,7 @@ static int cpu_map_bpf_prog_run_xdp(struct bpf_cpu_map_entry *rcpu,
                                    void **frames, int n,
                                    struct xdp_cpumap_stats *stats)
 {
-       struct xdp_rxq_info rxq;
+       struct xdp_rxq_info rxq = {};
        struct xdp_buff xdp;
        int i, nframes = 0;