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authorKonstantin Khlebnikov <khlebnikov@yandex-team.ru>2017-02-08 14:28:55 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-02-10 16:02:26 +0100
commit17627157cda13089d8a6c1c2d35acb07334b899c (patch)
tree9a717bcda9657c2e46943d852631e0a53fe3e45a
parent64e90a8acb8590c2468c919f803652f081e3a4bf (diff)
kernfs: handle null pointers while printing node name and path
Null kernfs nodes could be found at cgroups during construction. It seems safer to handle these null pointers right in kernfs in the same way as printf prints "(null)" for null pointer string. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/kernfs/dir.c10
-rw-r--r--include/trace/events/cgroup.h20
2 files changed, 16 insertions, 14 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index cf4c636ff4da..439b946c4808 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -41,6 +41,9 @@ static bool kernfs_lockdep(struct kernfs_node *kn)
static int kernfs_name_locked(struct kernfs_node *kn, char *buf, size_t buflen)
{
+ if (!kn)
+ return strlcpy(buf, "(null)", buflen);
+
return strlcpy(buf, kn->parent ? kn->name : "/", buflen);
}
@@ -110,6 +113,8 @@ static struct kernfs_node *kernfs_common_ancestor(struct kernfs_node *a,
* kn_to: /n1/n2/n3 [depth=3]
* result: /../..
*
+ * [3] when @kn_to is NULL result will be "(null)"
+ *
* Returns the length of the full path. If the full length is equal to or
* greater than @buflen, @buf contains the truncated path with the trailing
* '\0'. On error, -errno is returned.
@@ -123,6 +128,9 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
size_t depth_from, depth_to, len = 0;
int i, j;
+ if (!kn_to)
+ return strlcpy(buf, "(null)", buflen);
+
if (!kn_from)
kn_from = kernfs_root(kn_to)->kn;
@@ -166,6 +174,8 @@ static int kernfs_path_from_node_locked(struct kernfs_node *kn_to,
* similar to strlcpy(). It returns the length of @kn's name and if @buf
* isn't long enough, it's filled upto @buflen-1 and nul terminated.
*
+ * Fills buffer with "(null)" if @kn is NULL.
+ *
* This function can be called from any context.
*/
int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
diff --git a/include/trace/events/cgroup.h b/include/trace/events/cgroup.h
index ab68640a18d0..c226f50e88fa 100644
--- a/include/trace/events/cgroup.h
+++ b/include/trace/events/cgroup.h
@@ -61,19 +61,15 @@ DECLARE_EVENT_CLASS(cgroup,
__field( int, id )
__field( int, level )
__dynamic_array(char, path,
- cgrp->kn ? cgroup_path(cgrp, NULL, 0) + 1
- : strlen("(null)"))
+ cgroup_path(cgrp, NULL, 0) + 1)
),
TP_fast_assign(
__entry->root = cgrp->root->hierarchy_id;
__entry->id = cgrp->id;
__entry->level = cgrp->level;
- if (cgrp->kn)
- cgroup_path(cgrp, __get_dynamic_array(path),
- __get_dynamic_array_len(path));
- else
- __assign_str(path, "(null)");
+ cgroup_path(cgrp, __get_dynamic_array(path),
+ __get_dynamic_array_len(path));
),
TP_printk("root=%d id=%d level=%d path=%s",
@@ -119,8 +115,7 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
__field( int, dst_id )
__field( int, dst_level )
__dynamic_array(char, dst_path,
- dst_cgrp->kn ? cgroup_path(dst_cgrp, NULL, 0) + 1
- : strlen("(null)"))
+ cgroup_path(dst_cgrp, NULL, 0) + 1)
__field( int, pid )
__string( comm, task->comm )
),
@@ -129,11 +124,8 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
__entry->dst_root = dst_cgrp->root->hierarchy_id;
__entry->dst_id = dst_cgrp->id;
__entry->dst_level = dst_cgrp->level;
- if (dst_cgrp->kn)
- cgroup_path(dst_cgrp, __get_dynamic_array(dst_path),
- __get_dynamic_array_len(dst_path));
- else
- __assign_str(dst_path, "(null)");
+ cgroup_path(dst_cgrp, __get_dynamic_array(dst_path),
+ __get_dynamic_array_len(dst_path));
__entry->pid = task->pid;
__assign_str(comm, task->comm);
),