From 3093f8b52c38ddbf93b96eb592168eec2cd53fb9 Mon Sep 17 00:00:00 2001 From: Badari Pulavarty Date: Sun, 21 Aug 2022 18:08:53 +0000 Subject: [PATCH] UPSTREAM: mm/damon/dbgfs: avoid duplicate context directory creation 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. Bug: 254441685 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 (cherry picked from commit d26f60703606ab425eee9882b32a1781a8bed74d) Signed-off-by: Lee Jones Change-Id: I8951b95f41306818ef1b4a5789369a84d8ca2cf2 --- mm/damon/dbgfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c index 5b899601e56c..6a3121dca040 100644 --- a/mm/damon/dbgfs.c +++ b/mm/damon/dbgfs.c @@ -721,6 +721,9 @@ 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();