utils: Copying source filename to avoid missing info.

Some applications use information from LOOP_GET_STATUS64. The file associated with loop device is pointed inside structure field `lo_file_name`. The current code is setting up a loop device without this information. A legacy example of code checking this is cryptsetup: static char *_ioctl_backing_file(const char *loop) { struct loop_info64 lo64 = {0}; int loop_fd; loop_fd = open(loop, O_RDONLY); if (loop_fd < 0) return NULL; if (ioctl(loop_fd, LOOP_GET_STATUS64, &lo64) < 0) { close(loop_fd); return NULL; } lo64.lo_file_name[LO_NAME_SIZE-2] = '*'; lo64.lo_file_name[LO_NAME_SIZE-1] = 0; close(loop_fd); return strdup((char*)lo64.lo_file_name); } It will return an empty string because lo_file_name was not set. Signed-off-by: Julio Faracco <jcfaracco@gmail.com>

utils: Copying source filename to avoid missing info.
34a4e3a2 · Julio Faracco · Christian Brauner · 649529d6 · 34a4e3a2
Unverified Commit 34a4e3a2 authored Sep 05, 2019 by Julio Faracco Committed by Christian Brauner Dec 02, 2019
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utils.c src/lxc/utils.c +2 -0

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--- a/src/lxc/utils.c
+++ b/src/lxc/utils.c
@@ -1549,6 +1549,8 @@ int lxc_prepare_loop_dev(const char *source, char *loop_dev, int flags)
 	memset(&lo64, 0, sizeof(lo64));
 	lo64.lo_flags = flags;

+	strlcpy((char *)lo64.lo_file_name, source, LO_NAME_SIZE);
+
 	ret = ioctl(fd_loop, LOOP_SET_STATUS64, &lo64);
 	if (ret < 0) {
 		SYSERROR("Failed to set loop status64");