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FAILED: patch "[PATCH] ima: Fix use-after-free on a dentry's dname.name" failed to apply to 5.4-stable tree

PATCH [email protected] 1 participant 1 message Jun 19, 2024

Subsystems (4)
Stable branch Security (LSM) Integrity measurement architecture (IMA) Extended Verification Module (EVM)
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The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x be84f32bb2c981ca6709
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024061920-daycare-control-aa50@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From be84f32bb2c981ca670922e047cdde1488b233de Mon Sep 17 00:00:00 2001
From: Stefan Berger <[email protected]>
Date: Fri, 22 Mar 2024 10:03:12 -0400
Subject: [PATCH] ima: Fix use-after-free on a dentry's dname.name

->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/ open here
Signed-off-by Al Viro <[email protected]>
Signed-off-by Stefan Berger <[email protected]>
Signed-off-by Mimi Zohar <[email protected]>
security/integrity/ima/ima_api.c +12 -4
index b37d043d5748..1856981e33df 100644
@@ -245,8 +245,8 @@ int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file,
 	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 ima_max_digest_data hash;
+	struct name_snapshot filename;
 	struct kstat stat;
 	int result = 0;
 	int length;

@@ -317,9 +317,13 @@ int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file,
 		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;
 }

@@ -432,6 +436,7 @@ void ima_audit_measurement(struct ima_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();

@@ -445,7 +450,10 @@ const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
 	}
 
 	if (!pathname) {
-		strscpy(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;
 	}
security/integrity/ima/ima_template_lib.c +14 -3
index 6cd0add524cd..3b2cb8f1002e 100644
@@ -483,7 +483,10 @@ 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);
 

@@ -496,7 +499,10 @@ 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
 		/*

@@ -505,8 +511,13 @@ 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;
 }
 
 /*