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lib/namespace: don't try to mount rw /sys over a ro one

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It will fail with EPERM on Linux 4.15.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Acked-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
This commit is contained in:
Lubomir Rintel 2018-02-12 20:23:12 +01:00 committed by Stephen Hemminger
parent 6bfa7a6b0e
commit 8f0807023d
1 changed files with 19 additions and 3 deletions
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22
lib/namespace.c
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@ -7,6 +7,7 @@
* 2 of the License, or (at your option) any later version.
*/
#include <sys/statvfs.h>
#include <fcntl.h>
#include <dirent.h>
#include <limits.h>
@ -46,6 +47,8 @@ int netns_switch(char *name)
{
char net_path[PATH_MAX];
int netns;
unsigned long mountflags = 0;
struct statvfs fsstat;
snprintf(net_path, sizeof(net_path), "%s/%s", NETNS_RUN_DIR, name);
netns = open(net_path, O_RDONLY | O_CLOEXEC);
@ -73,12 +76,25 @@ int netns_switch(char *name)
strerror(errno));
return -1;
}
/* Mount a version of /sys that describes the network namespace */
if (umount2("/sys", MNT_DETACH) < 0) {
fprintf(stderr, "umount of /sys failed: %s\n", strerror(errno));
if (statvfs("/sys", &fsstat) < 0) {
fprintf(stderr, "could not stat /sys (not mounted?): %s\n",strerror(errno));
return -1;
}
if (mount(name, "/sys", "sysfs", 0, NULL) < 0) {
if (fsstat.f_flag & ST_RDONLY) {
/* If /sys is not writable (e.g. in a container), we can't
* unmount the old /sys instance, but we can still mount a new
* read-only instance over it. */
mountflags = MS_RDONLY;
} else {
if (umount2("/sys", MNT_DETACH) < 0) {
fprintf(stderr, "umount of /sys failed: %s\n", strerror(errno));
return -1;
}
}
if (mount(name, "/sys", "sysfs", mountflags, NULL) < 0) {
fprintf(stderr, "mount of /sys failed: %s\n",strerror(errno));
return -1;
}