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util: Don't try to fchown files opened as non-root

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When virFileOpenAs is called with VIR_FILE_OPEN_AS_UID flag and uid/gid
different from root/root while libvirtd is running as root, we fork a
new child, change its effective UID/GID to uid/gid and run
virFileOpenAsNoFork. It doesn't make any sense to fchown() the opened
file in this case since we already know that uid/gid can access the file
when open succeeds and one of the following situations may happen:

- the file is already owned by uid/gid and we skip fchown even before
  this patch
- the file is owned by uid but not gid because it was created in a
  directory with SETGID set, in which case it is desirable not to change
  the group
- the file may be owned by a completely different user and/or group
  because it was created on a root-squashed or even all-squashed NFS
  filesystem, in which case fchown would most likely fail anyway
This commit is contained in:
Jiri Denemark 2011-07-08 14:11:01 +02:00
parent 724819a10a
commit 2f4d2496a8
1 changed files with 20 additions and 12 deletions
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32
src/util/util.c
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@ -652,7 +652,6 @@ virFileOpenAsNoFork(const char *path, int openflags, mode_t mode,
{
int fd = -1;
int ret = 0;
struct stat st;
if ((fd = open(path, openflags, mode)) < 0) {
ret = -errno;
@ -660,18 +659,26 @@ virFileOpenAsNoFork(const char *path, int openflags, mode_t mode,
path);
goto error;
}
if (fstat(fd, &st) == -1) {
ret = -errno;
virReportSystemError(errno, _("stat of '%s' failed"), path);
goto error;
}
if (((st.st_uid != uid) || (st.st_gid != gid))
&& (fchown(fd, uid, gid) < 0)) {
ret = -errno;
virReportSystemError(errno, _("cannot chown '%s' to (%u, %u)"),
path, (unsigned int) uid, (unsigned int) gid);
goto error;
/* VIR_FILE_OPEN_AS_UID in flags means we are running in a child process
* owned by uid and gid */
if (!(flags & VIR_FILE_OPEN_AS_UID)) {
struct stat st;
if (fstat(fd, &st) == -1) {
ret = -errno;
virReportSystemError(errno, _("stat of '%s' failed"), path);
goto error;
}
if (((st.st_uid != uid) || (st.st_gid != gid))
&& (fchown(fd, uid, gid) < 0)) {
ret = -errno;
virReportSystemError(errno, _("cannot chown '%s' to (%u, %u)"),
path, (unsigned int) uid, (unsigned int) gid);
goto error;
}
}
if ((flags & VIR_FILE_OPEN_FORCE_PERMS)
&& (fchmod(fd, mode) < 0)) {
ret = -errno;
@ -757,6 +764,7 @@ virFileOpenAs(const char *path, int openflags, mode_t mode,
if ((!(flags & VIR_FILE_OPEN_AS_UID))
|| (getuid() != 0)
|| ((uid == 0) && (gid == 0))) {
flags &= ~VIR_FILE_OPEN_AS_UID;
return virFileOpenAsNoFork(path, openflags, mode, uid, gid, flags);
}