From aeb1f77c0fed3cf5ea63a712a529a173ed884af9 Mon Sep 17 00:00:00 2001
From: Peter Krempa <pkrempa@redhat.com>
Date: Mon, 19 May 2025 13:37:32 +0200
Subject: [PATCH] qemu: fd: Log information about passed file descriptor
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Log information (type, label, etc) about FDs passed to qemu via APIs
from this module.

This does "spill" the selinux library code into this module, but
acessing it via the security driver would require passing much more
context to this module. Since it's for logging only it can be easily
removed if necessary.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 src/qemu/qemu_fd.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)

diff --git a/src/qemu/qemu_fd.c b/src/qemu/qemu_fd.c
index 333f9b128e..ef0a8d8127 100644
--- a/src/qemu/qemu_fd.c
+++ b/src/qemu/qemu_fd.c
@@ -25,6 +25,11 @@
 #include "virfile.h"
 #include "virlog.h"
 
+/* Used strictly for logging selinux context of passed FD */
+#ifdef WITH_SECDRIVER_SELINUX
+# include <selinux/selinux.h>
+#endif
+
 #define VIR_FROM_THIS VIR_FROM_QEMU
 VIR_LOG_INIT("qemu.qemu_fd");
 
@@ -44,6 +49,56 @@ struct _qemuFDPass {
 };
 
 
+static void
+qemuFDPassLogFDInfo(const char *name,
+                    size_t idx,
+                    int fd)
+{
+    struct stat st;
+    const char *type = "error";
+    g_autofree char *selinux = NULL;
+    g_autofree char *tmp = NULL;
+
+    if (fstat(fd, &st) == 0) {
+        switch (st.st_mode & S_IFMT) {
+           case S_IFBLK:
+               type = "block";
+               break;
+           case S_IFCHR:
+               type = "char";
+               break;
+           case S_IFDIR:
+               type = "directory";
+               break;
+           case S_IFIFO:
+               type = "pipe";
+               break;
+           case S_IFLNK:
+               type = "symlink";
+               break;
+           case S_IFREG:
+               type = "file";
+               break;
+           case S_IFSOCK:
+               type = "socket";
+               break;
+           default:
+               type = tmp = g_strdup_printf("unknown:'0x%x')", st.st_mode & S_IFMT);
+               break;
+        }
+    }
+
+#ifdef WITH_SECDRIVER_SELINUX
+    ignore_value(fgetfilecon_raw(fd, &selinux));
+#else
+    selinux = g_strdup("N/A");
+#endif
+
+    VIR_DEBUG("passing fd:'%i', name:'%s'(%zu) type:'%s' selinux:'%s'",
+              fd, name, idx, type, selinux);
+}
+
+
 void
 qemuFDPassFree(qemuFDPass *fdpass)
 {
@@ -234,6 +289,8 @@ qemuFDPassTransferCommand(qemuFDPass *fdpass,
                                                fdpass->fds[i].fd,
                                                fdpass->fds[i].opaque);
 
+        qemuFDPassLogFDInfo(fdpass->fds[i].opaque, i, fdpass->fds[i].fd);
+
         virCommandPassFD(cmd, fdpass->fds[i].fd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
         fdpass->fds[i].fd = -1;
         virCommandAddArgList(cmd, "-add-fd", arg, NULL);
@@ -274,6 +331,8 @@ qemuFDPassTransferMonitor(qemuFDPass *fdpass,
     }
 
     for (i = 0; i < fdpass->nfds; i++) {
+        qemuFDPassLogFDInfo(fdpass->fds[i].opaque, i, fdpass->fds[i].fd);
+
         if (qemuMonitorAddFileHandleToSet(mon,
                                           fdpass->fds[i].fd,
                                           fdpass->fdSetID,
@@ -381,6 +440,7 @@ qemuFDPassDirectTransferCommand(qemuFDPassDirect *fdpass,
     if (!fdpass)
         return;
 
+    qemuFDPassLogFDInfo(fdpass->name, 0, fdpass->fd);
     virCommandPassFD(cmd, fdpass->fd, VIR_COMMAND_PASS_FD_CLOSE_PARENT);
     g_free(fdpass->name);
     fdpass->name = g_strdup_printf("%d", fdpass->fd);
@@ -403,6 +463,8 @@ qemuFDPassDirectTransferMonitor(qemuFDPassDirect *fdpass,
     if (!fdpass)
         return 0;
 
+    qemuFDPassLogFDInfo(fdpass->name, 0, fdpass->fd);
+
     if (qemuMonitorSendFileHandle(mon, fdpass->name, fdpass->fd) < 0)
         return -1;
 
-- 
2.47.3