New subject: [External] : Re: [PATCH 5.10.y 5.4.y] ima: Fix use-after-free on a dentry's dname.name

6 Feb 2025

From: Stefan Berger stefanb@linux.ibm.com
[ Upstream commit be84f32bb2c981ca670922e047cdde1488b233de ]
->d_name.name can change on rename and the earlier value can be freed;
there are conditions sufficient to stabilize it (->d_lock on dentry,
->d_lock on its parent, ->i_rwsem exclusive on the parent's inode,
rename_lock), but none of those are met at any of the sites. Take a stable
snapshot of the name instead.
Link: https://lore.kernel.org/all/20240202182732.GE2087318@ZenIV/
Signed-off-by: Al Viro viro@zeniv.linux.org.uk
Signed-off-by: Stefan Berger stefanb@linux.ibm.com
Signed-off-by: Mimi Zohar zohar@linux.ibm.com
[Samasth: bp to fix CVE-2024-39494; Minor conflict resolved due to code
context change]
Signed-off-by: Samasth Norway Ananda samasth.norway.ananda@oracle.com
---
 security/integrity/ima/ima_api.c          | 16 ++++++++++++----
 security/integrity/ima/ima_template_lib.c | 17 ++++++++++++++---
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index 70efd4aa1bd1..285d6069c32f 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -213,7 +213,7 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
    const char *audit_cause = "failed";
    struct inode *inode = file_inode(file);
    struct inode *real_inode = d_real_inode(file_dentry(file));
-	const char *filename = file->f_path.dentry->d_name.name;
+	struct name_snapshot filename;
    int result = 0;
    int length;
    void *tmpbuf;
@@ -276,9 +276,13 @@ int ima_collect_measurement(struct integrity_iint_cache *iint,
    	if (file->f_flags & O_DIRECT)
    		audit_cause = "failed(directio)";
+		take_dentry_name_snapshot(&filename, file->f_path.dentry);
+
    	integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
-				    filename, "collect_data", audit_cause,
-				    result, 0);
+				    filename.name.name, "collect_data",
+				    audit_cause, result, 0);
+
+		release_dentry_name_snapshot(&filename);
    }
    return result;
 }
@@ -391,6 +395,7 @@ void ima_audit_measurement(struct integrity_iint_cache *iint,
  */
 const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
 {
+	struct name_snapshot filename;
    char *pathname = NULL;
*pathbuf = __getname();
@@ -404,7 +409,10 @@ const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
    }
if (!pathname) {
-		strlcpy(namebuf, path->dentry->d_name.name, NAME_MAX);
+		take_dentry_name_snapshot(&filename, path->dentry);
+		strscpy(namebuf, filename.name.name, NAME_MAX);
+		release_dentry_name_snapshot(&filename);
+
    	pathname = namebuf;
    }
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index c022ee9e2a4e..f72a2564fd05 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -385,7 +385,10 @@ static int ima_eventname_init_common(struct ima_event_data *event_data,
    			     bool size_limit)
 {
    const char *cur_filename = NULL;
+	struct name_snapshot filename;
    u32 cur_filename_len = 0;
+	bool snapshot = false;
+	int ret;
BUG_ON(event_data->filename == NULL && event_data->file == NULL);
@@ -398,7 +401,10 @@ static int ima_eventname_init_common(struct ima_event_data *event_data,
    }
if (event_data->file) {
-		cur_filename = event_data->file->f_path.dentry->d_name.name;
+		take_dentry_name_snapshot(&filename,
+					  event_data->file->f_path.dentry);
+		snapshot = true;
+		cur_filename = filename.name.name;
    	cur_filename_len = strlen(cur_filename);
    } else
    	/*
@@ -407,8 +413,13 @@ static int ima_eventname_init_common(struct ima_event_data *event_data,
    	 */
    	cur_filename_len = IMA_EVENT_NAME_LEN_MAX;
 out:
-	return ima_write_template_field_data(cur_filename, cur_filename_len,
-					     DATA_FMT_STRING, field_data);
+	ret = ima_write_template_field_data(cur_filename, cur_filename_len,
+					    DATA_FMT_STRING, field_data);
+
+	if (snapshot)
+		release_dentry_name_snapshot(&filename);
+
+	return ret;
 }
/*
-- 
2.46.0



    

[PATCH 5.10.y 5.4.y] ima: Fix use-after-free on a dentry's dname.name

Note: The patch differs from the upstream commit: