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rbd: require global CAP_SYS_ADMIN for mapping and unmapping

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It turns out that currently we rely only on sysfs attribute
permissions:

  $ ll /sys/bus/rbd/{add*,remove*}
  --w------- 1 root root 4096 Sep  3 20:37 /sys/bus/rbd/add
  --w------- 1 root root 4096 Sep  3 20:37 /sys/bus/rbd/add_single_major
  --w------- 1 root root 4096 Sep  3 20:37 /sys/bus/rbd/remove
  --w------- 1 root root 4096 Sep  3 20:38 /sys/bus/rbd/remove_single_major

This means that images can be mapped and unmapped (i.e. block devices
can be created and deleted) by a UID 0 process even after it drops all
privileges or by any process with CAP_DAC_OVERRIDE in its user namespace
as long as UID 0 is mapped into that user namespace.

Be consistent with other virtual block devices (loop, nbd, dm, md, etc)
and require CAP_SYS_ADMIN in the initial user namespace for mapping and
unmapping, and also for dumping the configuration string and refreshing
the image header.

Cc: stable@vger.kernel.org
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
This commit is contained in:
Ilya Dryomov 2020-09-03 13:24:11 +02:00
parent f4d51dffc6
commit f44d04e696
1 changed files with 12 additions and 0 deletions
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12
drivers/block/rbd.c
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@ -5120,6 +5120,9 @@ static ssize_t rbd_config_info_show(struct device *dev,
{
struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
return sprintf(buf, "%s\n", rbd_dev->config_info);
}
@ -5231,6 +5234,9 @@ static ssize_t rbd_image_refresh(struct device *dev,
struct rbd_device *rbd_dev = dev_to_rbd_dev(dev);
int ret;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
ret = rbd_dev_refresh(rbd_dev);
if (ret)
return ret;
@ -7059,6 +7065,9 @@ static ssize_t do_rbd_add(struct bus_type *bus,
struct rbd_client *rbdc;
int rc;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!try_module_get(THIS_MODULE))
return -ENODEV;
@ -7209,6 +7218,9 @@ static ssize_t do_rbd_remove(struct bus_type *bus,
bool force = false;
int ret;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
dev_id = -1;
opt_buf[0] = '\0';
sscanf(buf, "%d %5s", &dev_id, opt_buf);