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kernfs: Convert kernfs_path_from_node_locked() from strlcpy() to strscpy()

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[ Upstream commit ff6d413b0b59466e5acf2e42f294b1842ae130a1 ]

One of the last remaining users of strlcpy() in the kernel is
kernfs_path_from_node_locked(), which passes back the problematic "length
we _would_ have copied" return value to indicate truncation.  Convert the
chain of all callers to use the negative return value (some of which
already doing this explicitly). All callers were already also checking
for negative return values, so the risk to missed checks looks very low.

In this analysis, it was found that cgroup1_release_agent() actually
didn't handle the "too large" condition, so this is technically also a
bug fix. :)

Here's the chain of callers, and resolution identifying each one as now
handling the correct return value:

kernfs_path_from_node_locked()
        kernfs_path_from_node()
                pr_cont_kernfs_path()
                        returns void
                kernfs_path()
                        sysfs_warn_dup()
                                return value ignored
                        cgroup_path()
                                blkg_path()
                                        bfq_bic_update_cgroup()
                                                return value ignored
                                TRACE_IOCG_PATH()
                                        return value ignored
                                TRACE_CGROUP_PATH()
                                        return value ignored
                                perf_event_cgroup()
                                        return value ignored
                                task_group_path()
                                        return value ignored
                                damon_sysfs_memcg_path_eq()
                                        return value ignored
                                get_mm_memcg_path()
                                        return value ignored
                                lru_gen_seq_show()
                                        return value ignored
                        cgroup_path_from_kernfs_id()
                                return value ignored
                cgroup_show_path()
                        already converted "too large" error to negative value
                cgroup_path_ns_locked()
                        cgroup_path_ns()
                                bpf_iter_cgroup_show_fdinfo()
                                        return value ignored
                                cgroup1_release_agent()
                                        wasn't checking "too large" error
                        proc_cgroup_show()
                                already converted "too large" to negative value

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Waiman Long <longman@redhat.com>
Cc: <cgroups@vger.kernel.org>
Co-developed-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Link: https://lore.kernel.org/r/20231116192127.1558276-3-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231212211741.164376-3-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Stable-dep-of: 1be59c97c83c ("cgroup/cpuset: Prevent UAF in proc_cpuset_show()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Kees Cook
2023-12-12 13:17:40 -08:00
committed by Greg Kroah-Hartman
parent c8a36455a0
commit aea95c68b7
4 changed files with 21 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
kernel/cgroup/cgroup-v1.c
View File

@@ -802,7 +802,7 @@ void cgroup1_release_agent(struct work_struct *work)
goto out_free;
ret = cgroup_path_ns(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
if (ret < 0 || ret >= PATH_MAX)
if (ret < 0)
goto out_free;
argv[0] = agentbuf;

4
kernel/cgroup/cgroup.c
View File

@@ -1887,7 +1887,7 @@ int cgroup_show_path(struct seq_file *sf, struct kernfs_node *kf_node,
len = kernfs_path_from_node(kf_node, ns_cgroup->kn, buf, PATH_MAX);
spin_unlock_irq(&css_set_lock);
if (len >= PATH_MAX)
if (len == -E2BIG)
len = -ERANGE;
else if (len > 0) {
seq_escape(sf, buf, " \t\n\\");
@@ -6277,7 +6277,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
if (cgroup_on_dfl(cgrp) || !(tsk->flags & PF_EXITING)) {
retval = cgroup_path_ns_locked(cgrp, buf, PATH_MAX,
current->nsproxy->cgroup_ns);
if (retval >= PATH_MAX)
if (retval == -E2BIG)
retval = -ENAMETOOLONG;
if (retval < 0)
goto out_unlock;

2
kernel/cgroup/cpuset.c
View File

@@ -4297,7 +4297,7 @@ int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
retval = cgroup_path_ns(css->cgroup, buf, PATH_MAX,
current->nsproxy->cgroup_ns);
css_put(css);
if (retval >= PATH_MAX)
if (retval == -E2BIG)
retval = -ENAMETOOLONG;
if (retval < 0)
goto out_free;