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fsdev-proxy-helper: avoid TOC/TOU race

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There is a minor time of check/time of use race between statfs and chroot.
It can be fixed easily by stat-ing the root after it has been changed.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
This commit is contained in:
Paolo Bonzini 2015-11-27 12:43:05 +01:00 committed by Greg Kurz
parent 714487515d
commit 49f817caaf
1 changed files with 10 additions and 10 deletions
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20
fsdev/virtfs-proxy-helper.c
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@ -1128,10 +1128,19 @@ int main(int argc, char **argv)
}
}
if (chdir("/") < 0) {
do_perror("chdir");
goto error;
}
if (chroot(rpath) < 0) {
do_perror("chroot");
goto error;
}
get_version = false;
#ifdef FS_IOC_GETVERSION
/* check whether underlying FS support IOC_GETVERSION */
retval = statfs(rpath, &st_fs);
retval = statfs("/", &st_fs);
if (!retval) {
switch (st_fs.f_type) {
case EXT2_SUPER_MAGIC:
@ -1144,16 +1153,7 @@ int main(int argc, char **argv)
}
#endif
if (chdir("/") < 0) {
do_perror("chdir");
goto error;
}
if (chroot(rpath) < 0) {
do_perror("chroot");
goto error;
}
umask(0);
if (init_capabilities() < 0) {
goto error;
}