6.12-stable review patch. If anyone has any objections, please let me know.
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From: Christian Brauner brauner@kernel.org
commit c1f86d0ac322c7e77f6f8dbd216c65d39358ffc0 upstream.
Massage listmount() and make sure we don't call path_put() under the namespace semaphore. If we put the last reference we're fscked.
Fixes: b4c2bea8ceaa ("add listmount(2) syscall") Cc: stable@vger.kernel.org # v6.8+ Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/namespace.c | 87 ++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 59 insertions(+), 28 deletions(-)
--- a/fs/namespace.c +++ b/fs/namespace.c @@ -5411,23 +5411,34 @@ retry: return ret; }
-static ssize_t do_listmount(struct mnt_namespace *ns, u64 mnt_parent_id, - u64 last_mnt_id, u64 *mnt_ids, size_t nr_mnt_ids, - bool reverse) +struct klistmount { + u64 last_mnt_id; + u64 mnt_parent_id; + u64 *kmnt_ids; + u32 nr_mnt_ids; + struct mnt_namespace *ns; + struct path root; +}; + +static ssize_t do_listmount(struct klistmount *kls, bool reverse) { - struct path root __free(path_put) = {}; + struct mnt_namespace *ns = kls->ns; + u64 mnt_parent_id = kls->mnt_parent_id; + u64 last_mnt_id = kls->last_mnt_id; + u64 *mnt_ids = kls->kmnt_ids; + size_t nr_mnt_ids = kls->nr_mnt_ids; struct path orig; struct mount *r, *first; ssize_t ret;
rwsem_assert_held(&namespace_sem);
- ret = grab_requested_root(ns, &root); + ret = grab_requested_root(ns, &kls->root); if (ret) return ret;
if (mnt_parent_id == LSMT_ROOT) { - orig = root; + orig = kls->root; } else { orig.mnt = lookup_mnt_in_ns(mnt_parent_id, ns); if (!orig.mnt) @@ -5439,7 +5450,7 @@ static ssize_t do_listmount(struct mnt_n * Don't trigger audit denials. We just want to determine what * mounts to show users. */ - if (!is_path_reachable(real_mount(orig.mnt), orig.dentry, &root) && + if (!is_path_reachable(real_mount(orig.mnt), orig.dentry, &kls->root) && !ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN)) return -EPERM;
@@ -5472,14 +5483,45 @@ static ssize_t do_listmount(struct mnt_n return ret; }
+static void __free_klistmount_free(const struct klistmount *kls) +{ + path_put(&kls->root); + kvfree(kls->kmnt_ids); + mnt_ns_release(kls->ns); +} + +static inline int prepare_klistmount(struct klistmount *kls, struct mnt_id_req *kreq, + size_t nr_mnt_ids) +{ + + u64 last_mnt_id = kreq->param; + + /* The first valid unique mount id is MNT_UNIQUE_ID_OFFSET + 1. */ + if (last_mnt_id != 0 && last_mnt_id <= MNT_UNIQUE_ID_OFFSET) + return -EINVAL; + + kls->last_mnt_id = last_mnt_id; + + kls->nr_mnt_ids = nr_mnt_ids; + kls->kmnt_ids = kvmalloc_array(nr_mnt_ids, sizeof(*kls->kmnt_ids), + GFP_KERNEL_ACCOUNT); + if (!kls->kmnt_ids) + return -ENOMEM; + + kls->ns = grab_requested_mnt_ns(kreq); + if (!kls->ns) + return -ENOENT; + + kls->mnt_parent_id = kreq->mnt_id; + return 0; +} + SYSCALL_DEFINE4(listmount, const struct mnt_id_req __user *, req, u64 __user *, mnt_ids, size_t, nr_mnt_ids, unsigned int, flags) { - u64 *kmnt_ids __free(kvfree) = NULL; + struct klistmount kls __free(klistmount_free) = {}; const size_t maxcount = 1000000; - struct mnt_namespace *ns __free(mnt_ns_release) = NULL; struct mnt_id_req kreq; - u64 last_mnt_id; ssize_t ret;
if (flags & ~LISTMOUNT_REVERSE) @@ -5500,31 +5542,20 @@ SYSCALL_DEFINE4(listmount, const struct if (ret) return ret;
- last_mnt_id = kreq.param; - /* The first valid unique mount id is MNT_UNIQUE_ID_OFFSET + 1. */ - if (last_mnt_id != 0 && last_mnt_id <= MNT_UNIQUE_ID_OFFSET) - return -EINVAL; - - kmnt_ids = kvmalloc_array(nr_mnt_ids, sizeof(*kmnt_ids), - GFP_KERNEL_ACCOUNT); - if (!kmnt_ids) - return -ENOMEM; - - ns = grab_requested_mnt_ns(&kreq); - if (!ns) - return -ENOENT; + ret = prepare_klistmount(&kls, &kreq, nr_mnt_ids); + if (ret) + return ret;
- if (kreq.mnt_ns_id && (ns != current->nsproxy->mnt_ns) && - !ns_capable_noaudit(ns->user_ns, CAP_SYS_ADMIN)) + if (kreq.mnt_ns_id && (kls.ns != current->nsproxy->mnt_ns) && + !ns_capable_noaudit(kls.ns->user_ns, CAP_SYS_ADMIN)) return -ENOENT;
scoped_guard(rwsem_read, &namespace_sem) - ret = do_listmount(ns, kreq.mnt_id, last_mnt_id, kmnt_ids, - nr_mnt_ids, (flags & LISTMOUNT_REVERSE)); + ret = do_listmount(&kls, (flags & LISTMOUNT_REVERSE)); if (ret <= 0) return ret;
- if (copy_to_user(mnt_ids, kmnt_ids, ret * sizeof(*mnt_ids))) + if (copy_to_user(mnt_ids, kls.kmnt_ids, ret * sizeof(*mnt_ids))) return -EFAULT;
return ret;