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atomically replace existing nodes and symlinks

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Based on a patch from Scott James Remnant <scott@ubuntu.com>.
This commit is contained in:
Kay Sievers 2007-06-21 02:28:09 +02:00
parent 3b62a56903
commit e54f0b4ad2
1 changed files with 77 additions and 31 deletions
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108
udev_node.c
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@ -33,9 +33,11 @@
#include "udev_rules.h"
#include "udev_selinux.h"
#define TMP_FILE_EXT ".udev-tmp"
int udev_node_mknod(struct udevice *udev, const char *file, dev_t devt, mode_t mode, uid_t uid, gid_t gid)
{
char file_tmp[PATH_SIZE + sizeof(TMP_FILE_EXT)];
struct stat stats;
int retval = 0;
@ -44,28 +46,37 @@ int udev_node_mknod(struct udevice *udev, const char *file, dev_t devt, mode_t m
else
mode |= S_IFCHR;
if (lstat(file, &stats) != 0)
goto create;
/* preserve node with already correct numbers, to prevent changing the inode number */
if ((stats.st_mode & S_IFMT) == (mode & S_IFMT) && (stats.st_rdev == devt)) {
info("preserve file '%s', because it has correct dev_t", file);
selinux_setfilecon(file, udev->dev->kernel, stats.st_mode);
goto perms;
if (lstat(file, &stats) == 0) {
if ((stats.st_mode & S_IFMT) == (mode & S_IFMT) && (stats.st_rdev == devt)) {
info("preserve file '%s', because it has correct dev_t", file);
selinux_setfilecon(file, udev->dev->kernel, stats.st_mode);
goto perms;
}
}
if (unlink(file) != 0)
err("unlink(%s) failed: %s", file, strerror(errno));
else
dbg("already present file '%s' unlinked", file);
create:
selinux_setfscreatecon(file, udev->dev->kernel, mode);
retval = mknod(file, mode, devt);
selinux_resetfscreatecon();
if (retval == 0)
goto perms;
info("atomically replace '%s'", file);
strlcpy(file_tmp, file, sizeof(file_tmp));
strlcat(file_tmp, TMP_FILE_EXT, sizeof(file_tmp));
selinux_setfscreatecon(file_tmp, udev->dev->kernel, mode);
retval = mknod(file_tmp, mode, devt);
selinux_resetfscreatecon();
if (retval != 0) {
err("mknod(%s, %#o, %u, %u) failed: %s",
file, mode, major(devt), minor(devt), strerror(errno));
file_tmp, mode, major(devt), minor(devt), strerror(errno));
goto exit;
}
retval = rename(file_tmp, file);
if (retval != 0) {
err("rename(%s, %s) failed: %s",
file_tmp, file, strerror(errno));
unlink(file_tmp);
goto exit;
}
@ -84,18 +95,19 @@ perms:
goto exit;
}
}
exit:
return retval;
}
static int node_symlink(const char *node, const char *slink)
{
struct stat stats;
char target[PATH_SIZE] = "";
char buf[PATH_SIZE];
char slink_tmp[PATH_SIZE + sizeof(TMP_FILE_EXT)];
int i = 0;
int tail = 0;
int len;
int retval = 0;
/* use relative link */
while (node[i] && (node[i] == slink[i])) {
@ -110,28 +122,62 @@ static int node_symlink(const char *node, const char *slink)
}
strlcat(target, &node[tail], sizeof(target));
/* look if symlink already exists */
len = readlink(slink, buf, sizeof(buf));
if (len > 0) {
buf[len] = '\0';
if (strcmp(target, buf) == 0) {
info("preserve already existing symlink '%s' to '%s'", slink, target);
selinux_setfilecon(slink, NULL, S_IFLNK);
goto exit;
/* preserve link with correct target, do not replace node of other device */
if (lstat(slink, &stats) == 0) {
if (S_ISBLK(stats.st_mode) || S_ISCHR(stats.st_mode)) {
struct stat stats2;
info("found existing node instead of symlink '%s'", slink);
if (lstat(node, &stats2) == 0) {
if ((stats.st_mode & S_IFMT) == (stats2.st_mode & S_IFMT) &&
stats.st_rdev == stats2.st_rdev) {
info("replace device node '%s' with symlink to our node '%s'", slink, node);
} else {
err("device node '%s' already exists, link '%s' will not overwrite it", node, slink);
goto exit;
}
}
} else if (S_ISLNK(stats.st_mode)) {
char buf[PATH_SIZE];
info("found existing symlink '%s'", slink);
len = readlink(slink, buf, sizeof(buf));
if (len > 0) {
buf[len] = '\0';
if (strcmp(target, buf) == 0) {
info("preserve already existing symlink '%s' to '%s'", slink, target);
selinux_setfilecon(slink, NULL, S_IFLNK);
goto exit;
}
}
}
info("link '%s' points to different target '%s', delete it", slink, buf);
unlink(slink);
}
/* create link */
info("creating symlink '%s' to '%s'", slink, target);
selinux_setfscreatecon(slink, NULL, S_IFLNK);
if (symlink(target, slink) != 0)
err("symlink(%s, %s) failed: %s", target, slink, strerror(errno));
retval = symlink(target, slink);
selinux_resetfscreatecon();
if (retval == 0)
goto exit;
info("atomically replace '%s'", slink);
strlcpy(slink_tmp, slink, sizeof(slink_tmp));
strlcat(slink_tmp, TMP_FILE_EXT, sizeof(slink_tmp));
selinux_setfscreatecon(slink_tmp, NULL, S_IFLNK);
retval = symlink(target, slink_tmp);
selinux_resetfscreatecon();
if (retval != 0) {
err("symlink(%s, %s) failed: %s", target, slink_tmp, strerror(errno));
goto exit;
}
retval = rename(slink_tmp, slink);
if (retval != 0) {
err("rename(%s, %s) failed: %s", slink_tmp, slink, strerror(errno));
unlink(slink_tmp);
goto exit;
}
exit:
return 0;
return retval;
}
static int update_link(struct udevice *udev, const char *name)
@ -303,7 +349,7 @@ int udev_node_add(struct udevice *udev)
gid = lookup_group(udev->group);
}
info("creating device node '%s', major = '%d', minor = '%d', " "mode = '%#o', uid = '%d', gid = '%d'",
info("creating device node '%s', major=%d, minor=%d, mode=%#o, uid=%d, gid=%d",
filename, major(udev->devt), minor(udev->devt), udev->mode, uid, gid);
if (!udev->test_run)