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=== Description (from pull-request) ===
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.
v1: missing string casting for `lo_file_name`.
Signed-off-by: Julio Faracco <jcfara...@gmail.com>
From a70c9e85a6d8ac1b75d6705d2373fd9c7b567240 Mon Sep 17 00:00:00 2001
From: Julio Faracco <jcfara...@gmail.com>
Date: Thu, 5 Sep 2019 01:43:21 -0300
Subject: [PATCH] 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 <jcfara...@gmail.com>
---
src/lxc/utils.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/src/lxc/utils.c b/src/lxc/utils.c
index 9ddbabfc85..02fe40a235 100644
--- a/src/lxc/utils.c
+++ b/src/lxc/utils.c
@@ -1557,6 +1557,8 @@ 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");
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