fix: check length in SkBuff's load_bytes function

ebpf/aya-ebpf/src/programs/sk_buff.rs

@@ -86,6 +86,10 @@ impl SkBuff {
         let len = usize::try_from(self.len()).map_err(|core::num::TryFromIntError { .. }| -1)?;
         let len = len.checked_sub(offset).ok_or(-1)?;
         let len = len.min(dst.len());
+        if len == 0 {
+            return Ok(0);
+        }
+
         let len_u32 = u32::try_from(len).map_err(|core::num::TryFromIntError { .. }| -1)?;
         let ret = unsafe {
             bpf_skb_load_bytes(

test/integration-ebpf/src/test.rs

@@ -5,11 +5,12 @@
 use aya_ebpf::{
     bindings::{bpf_ret_code, xdp_action},
     macros::{
-        flow_dissector, kprobe, kretprobe, lsm, lsm_cgroup, tracepoint, uprobe, uretprobe, xdp,
+        flow_dissector, kprobe, kretprobe, lsm, lsm_cgroup, socket_filter, tracepoint, uprobe,
+        uretprobe, xdp,
     },
     programs::{
-        FlowDissectorContext, LsmContext, ProbeContext, RetProbeContext, TracePointContext,
-        XdpContext,
+        FlowDissectorContext, LsmContext, ProbeContext, RetProbeContext, SkBuffContext,
+        TracePointContext, XdpContext,
     },
 };
 #[cfg(not(test))]
@@ -61,3 +62,12 @@ const fn test_lsm(_ctx: LsmContext) -> i32 {
 const fn test_lsm_cgroup(_ctx: LsmContext) -> i32 {
     0 // Disallow.
 }
+
+#[socket_filter]
+fn fix_test_load_bytes(ctx: SkBuffContext) -> i64 {
+    let mut buf = [0u8; 4];
+    match ctx.load_bytes(2, &mut buf) {
+        Ok(_) => 1,
+        Err(_) => 0,
+    }
+}

test/integration-test/src/tests.rs

@@ -18,6 +18,7 @@ mod info;
 mod iter;
 mod linear_data_structures;
 mod load;
+mod load_bytes;
 mod log;
 mod lsm;
 mod map_pin;

test/integration-test/src/tests/load_bytes.rs

@@ -0,0 +1,24 @@
+use aya::{
+    Ebpf,
+    programs::{ProgramType, SocketFilter},
+    sys::is_program_supported,
+};
+
+// Load the eBPF socket filter program from the embedded bytes and ensure it loads
+// successfully (i.e., passes verification) using Ebpf::load and prog.load().
+#[test_log::test]
+fn test_load_bytes() {
+    if !is_program_supported(ProgramType::SocketFilter).unwrap() {
+        eprintln!("skipping test - socket_filter program not supported");
+        return;
+    }
+
+    let mut bpf: Ebpf = Ebpf::load(crate::TEST).unwrap();
+    let prog: &mut SocketFilter = bpf
+        .program_mut("fix_test_load_bytes")
+        .unwrap()
+        .try_into()
+        .unwrap();
+    prog.load().unwrap();
+    // should pass verification
+}