Commit d26f6070 authored by Badari Pulavarty's avatar Badari Pulavarty Committed by Andrew Morton

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.

Link: https://lkml.kernel.org/r/20220821180853.2400-1-sj@kernel.org
Fixes: 75c1c2b5 ("mm/damon/dbgfs: support multiple contexts")
Signed-off-by: default avatarBadari Pulavarty <badari.pulavarty@intel.com>
Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>	[ 5.15.x]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent ac733f65
...@@ -818,6 +818,9 @@ static int dbgfs_mk_context(char *name) ...@@ -818,6 +818,9 @@ static int dbgfs_mk_context(char *name)
return -ENOENT; return -ENOENT;
new_dir = debugfs_create_dir(name, root); 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; dbgfs_dirs[dbgfs_nr_ctxs] = new_dir;
new_ctx = dbgfs_new_ctx(); new_ctx = dbgfs_new_ctx();
......
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