[libvirt] [PATCH] util: Don't try to fchown files opened as non-root
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
---
src/util/util.c | 31 +++++++++++++++++++------------
1 files changed, 19 insertions(+), 12 deletions(-)
diff --git a/src/util/util.c b/src/util/util.c
index 3d0ceea..8ff25da 100644
--- a/src/util/util.c
+++ b/src/util/util.c
@@ -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 +659,25 @@ 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 +763,7 @@ 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);
}
--
1.7.6