From ddcb0696136b9af1c8d489fd4763e12f52864b95 Mon Sep 17 00:00:00 2001 From: Badari Pulavarty Date: Sun, 21 Aug 2022 18:08:53 +0000 Subject: [PATCH] mm/damon/dbgfs: avoid duplicate context directory creation commit d26f60703606ab425eee9882b32a1781a8bed74d upstream. 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. Link: https://lkml.kernel.org/r/20220821180853.2400-1-sj@kernel.org Fixes: 75c1c2b53c78 ("mm/damon/dbgfs: support multiple contexts") Signed-off-by: Badari Pulavarty Signed-off-by: SeongJae Park Cc: [ 5.15.x] Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/damon/dbgfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c index 3662499..70a5cb9 100644 --- a/mm/damon/dbgfs.c +++ b/mm/damon/dbgfs.c @@ -376,6 +376,9 @@ 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(); -- 2.7.4