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
--
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