Re: [libvirt] [PATCH 2/3] New utility functions virFileCreate and virDirCreate

Quoting Serge E. Hallyn (serue(a)us.ibm.com): > Quoting Laine Stump (laine(a)laine.org): > >> These functions create a new file or directory with the given >> uid/gid. If the flag VIR_FILE_CREATE_AS_UID is given, they do this by >> forking a new process, calling setuid/setgid in the new process, and >> then creating the file. This is better than simply calling open then >> fchown, because in the latter case, a root-squashing nfs server would >> create the new file as user nobody, then refuse to allow fchown. >> >> If VIR_FILE_CREATE_AS_UID is not specified, the simpler tactic of >> creating the file/dir, then chowning is is used. This gives better >> results in cases where the parent directory isn't on a root-squashing >> NFS server, but doesn't give permission for the specified uid/gid to >> create files. (Note that if the fork/setuid method fails to create the >> file due to access privileges, the parent process will make a second >> attempt using this simpler method.) >> >> Return from both of these functions is 0 on success, or the value of >> errno if there was a failure. >> --- >> src/util/util.c | 247 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ >> src/util/util.h | 9 ++ >> 2 files changed, 256 insertions(+), 0 deletions(-) >> >> diff --git a/src/util/util.c b/src/util/util.c >> index 1d493de..1cb29f4 100644 >> --- a/src/util/util.c >> +++ b/src/util/util.c >> @@ -1126,6 +1126,253 @@ int virFileExists(const char *path) >> return(0); >> } >> >> + >> +static int virFileCreateSimple(const char *path, mode_t mode, uid_t uid, gid_t gid) { >> + int fd = -1; >> + int ret = 0; >> + >> + if ((fd = open(path, O_RDWR | O_CREAT | O_EXCL, mode))< 0) { >> + ret = errno; >> + virReportSystemError(NULL, errno, _("failed to create file '%s'"), >> + path); >> + goto error; >> + } >> + if ((getuid() == 0)&& ((uid != 0) || (gid != 0))) { >> > How about checking for CAP_CHOWN instead of getuid()==0? Otherwise > if I try installing this certain ways, virFileCreateSimple() will refuse > to try the chown even though it could succeed. > I guess for certain netfs's the uid might matter more, so checking for either condition - or in fact just trying the fchown, then doing a stat, then making sure st.st_{ug}id are correct after the fact - seems useful.