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fs: Allow statmount() in foreign mount namespace

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This patch makes use of the new mnt_ns_id field in struct mnt_id_req to
allow users to stat mount entries not in their mount namespace.  The
rules are the same as listmount(), the user must have CAP_SYS_ADMIN in
their user namespace and the target mount namespace must be a child of
the current namespace.

Co-developed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/52a2e17e50ba7aa420bc8bae1d9e88ff593395c1.1719243756.git.josef@toxicpanda.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2024-06-24 11:49:49 -04:00
parent 0a3deb1185
commit 71aacb4c8c
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 25 additions and 6 deletions
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31
fs/namespace.c
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@ -4974,10 +4974,8 @@ static int statmount_fs_type(struct kstatmount *s, struct seq_file *seq)
return 0;
}
static void statmount_mnt_ns_id(struct kstatmount *s)
static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns)
{
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
s->sm.mask |= STATMOUNT_MNT_NS_ID;
s->sm.mnt_ns_id = ns->seq;
}
@ -5079,7 +5077,7 @@ static int do_statmount(struct kstatmount *s)
err = statmount_string(s, STATMOUNT_MNT_POINT);
if (!err && s->mask & STATMOUNT_MNT_NS_ID)
statmount_mnt_ns_id(s);
statmount_mnt_ns_id(s, ns);
if (err)
return err;
@ -5196,6 +5194,7 @@ SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req,
struct statmount __user *, buf, size_t, bufsize,
unsigned int, flags)
{
struct mnt_namespace *ns __free(mnt_ns_release) = NULL;
struct vfsmount *mnt;
struct mnt_id_req kreq;
struct kstatmount ks;
@ -5210,13 +5209,28 @@ SYSCALL_DEFINE4(statmount, const struct mnt_id_req __user *, req,
if (ret)
return ret;
ns = grab_requested_mnt_ns(kreq.mnt_ns_id);
if (!ns)
return -ENOENT;
if (kreq.mnt_ns_id && (ns != current->nsproxy->mnt_ns) &&
!ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN))
return -ENOENT;
retry:
ret = prepare_kstatmount(&ks, &kreq, buf, bufsize, seq_size);
if (ret)
return ret;
down_read(&namespace_sem);
mnt = lookup_mnt_in_ns(kreq.mnt_id, current->nsproxy->mnt_ns);
/* Has the namespace already been emptied? */
if (kreq.mnt_ns_id && RB_EMPTY_ROOT(&ns->mounts)) {
up_read(&namespace_sem);
kvfree(ks.seq.buf);
return -ENOENT;
}
mnt = lookup_mnt_in_ns(kreq.mnt_id, ns);
if (!mnt) {
up_read(&namespace_sem);
kvfree(ks.seq.buf);
@ -5224,7 +5238,12 @@ retry:
}
ks.mnt = mnt;
get_fs_root(current->fs, &ks.root);
ret = grab_requested_root(ns, &ks.root);
if (ret) {
up_read(&namespace_sem);
kvfree(ks.seq.buf);
return ret;
}
ret = do_statmount(&ks);
path_put(&ks.root);
up_read(&namespace_sem);