rust: fix fd_get() pointer dereference

All fd_get() functions in the Rust bindings were returning the pointer
address cast to i32 instead of dereferencing the pointer to retrieve
the actual file descriptor value.

The C API signature is:
  cs_error_t xxx_fd_get(xxx_handle_t handle, int *fd);

Where fd is an output parameter - the C library writes the file
descriptor into the memory pointed to by fd. The Rust wrapper must
dereference this pointer to get the value.

Before (WRONG):
  Ok(c_fd as i32)  // Returns pointer address, e.g.
    0xe60d9018 = -435318760

After (CORRECT):
  Ok(unsafe { *c_fd })  // Returns actual fd value, e.g. 5

This bug caused "Bad file descriptor (os error 9)" errors when trying
to register the returned "file descriptors" with event loops (epoll,
tokio AsyncFd, etc.), as the values were actually stack addresses.

Affected functions:
- bindings/rust/src/cfg.rs:169 - corosync_cfg_fd_get
- bindings/rust/src/cmap.rs:152 - cmap_fd_get
- bindings/rust/src/cpg.rs:384 - cpg_fd_get
- bindings/rust/src/quorum.rs:238 - quorum_fd_get
- bindings/rust/src/votequorum.rs:271 - votequorum_fd_get

Signed-off-by: Kefu Chai <k.chai@proxmox.com>
Reviewed-by: Christine Caulfield <ccaulfie@redhat.com>

bindings/rust/src/cfg.rs

@@ -166,7 +166,7 @@ pub fn fd_get(handle: &Handle) -> Result<i32> {
     let c_fd: *mut c_int = &mut 0 as *mut _ as *mut c_int;
     let res = unsafe { ffi::corosync_cfg_fd_get(handle.cfg_handle, c_fd) };
     if res == ffi::CS_OK {
-        Ok(c_fd as i32)
+        Ok(unsafe { *c_fd })
     } else {
         Err(CsError::from_c(res))
     }

bindings/rust/src/cmap.rs

@@ -149,7 +149,7 @@ pub fn fd_get(handle: &Handle) -> Result<i32> {
     let c_fd: *mut c_int = &mut 0 as *mut _ as *mut c_int;
     let res = unsafe { ffi::cmap_fd_get(handle.cmap_handle, c_fd) };
     if res == ffi::CS_OK {
-        Ok(c_fd as i32)
+        Ok(unsafe { *c_fd })
     } else {
         Err(CsError::from_c(res))
     }

bindings/rust/src/cpg.rs

@@ -381,7 +381,7 @@ pub fn fd_get(handle: &Handle) -> Result<i32> {
     let c_fd: *mut c_int = &mut 0 as *mut _ as *mut c_int;
     let res = unsafe { ffi::cpg_fd_get(handle.cpg_handle, c_fd) };
     if res == ffi::CS_OK {
-        Ok(c_fd as i32)
+        Ok(unsafe { *c_fd })
     } else {
         Err(CsError::from_c(res))
     }

bindings/rust/src/quorum.rs

@@ -235,7 +235,7 @@ pub fn fd_get(handle: &Handle) -> Result<i32> {
     let c_fd: *mut c_int = &mut 0 as *mut _ as *mut c_int;
     let res = unsafe { ffi::quorum_fd_get(handle.quorum_handle, c_fd) };
     if res == ffi::CS_OK {
-        Ok(c_fd as i32)
+        Ok(unsafe { *c_fd })
     } else {
         Err(CsError::from_c(res))
     }

bindings/rust/src/votequorum.rs

@@ -268,7 +268,7 @@ pub fn fd_get(handle: &Handle) -> Result<i32> {
     let c_fd: *mut c_int = &mut 0 as *mut _ as *mut c_int;
     let res = unsafe { ffi::votequorum_fd_get(handle.votequorum_handle, c_fd) };
     if res == ffi::CS_OK {
-        Ok(c_fd as i32)
+        Ok(unsafe { *c_fd })
     } else {
         Err(CsError::from_c(res))
     }