mm-damon-dbgfs-avoid-duplicate-context-directory-creation.patch removed from -mm tree

The quilt patch titled
Subject: mm/damon/dbgfs: avoid duplicate context directory creation
has been removed from the -mm tree. Its filename was
mm-damon-dbgfs-avoid-duplicate-context-directory-creation.patch

This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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From: Badari Pulavarty <[email protected]>
Subject: mm/damon/dbgfs: avoid duplicate context directory creation
Date: Sun, 21 Aug 2022 18:08:53 +0000

When user tries to create a DAMON context via the DAMON debugfs interface with a name of an already existing context, the context directory creation fails but a new context is created and added in the internal data structure, due to absence of the directory creation success check. As a result, memory could leak and DAMON cannot be turned on. An example test case is as below:

    # cd /sys/kernel/debug/damon/
    # echo "off" >  monitor_on
    # echo paddr > target_ids
    # echo "abc" > mk_context
    # echo "abc" > mk_context
    # echo $$ > abc/target_ids
    # echo "on" > monitor_on  <<< fails

Return value of 'debugfs_create_dir()' is expected to be ignored in general, but this is an exceptional case as DAMON feature is depending on the debugfs functionality and it has the potential duplicate name issue. This commit therefore fixes the issue by checking the directory creation failure and immediately return the error in the case.

---

 mm/damon/dbgfs.c |    3 +++
 1 file changed, 3 insertions(+)

@@ -818,6 +818,9 @@ static int dbgfs_mk_context(char *name)
 		return -ENOENT;
 
 	new_dir = debugfs_create_dir(name, root);
+	/* Below check is required for a potential duplicated name case */
+	if (IS_ERR(new_dir))
+		return PTR_ERR(new_dir);
 	dbgfs_dirs[dbgfs_nr_ctxs] = new_dir;
 
 	new_ctx = dbgfs_new_ctx();

_

Patches currently in -mm which might be from [email protected] are