The miscdev kunit suite registers two miscdevices with the same name and expects -EEXIST. The second call currently goes all the way to sysfs_create_dir_ns(), which prints "cannot create duplicate filename" with a backtrace on every run.
Walk misc_list under misc_mtx, return -EEXIST on a name collision and free the just-allocated minor before returning. To: Arnd Bergmann <[email protected]> To: Greg Kroah-Hartman <[email protected]> Signed-off-by: Jia He <[email protected]> --- drivers/char/misc.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/char/misc.c b/drivers/char/misc.c index 726516fb0a3b..d6ffa21ac495 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -248,6 +248,28 @@ int misc_register(struct miscdevice *misc) } } + /* + * Detect duplicate names up-front so the subsequent + * device_create_with_groups() does not trip + * sysfs_create_dir_ns()->sysfs_warn_dup(), which unconditionally + * dumps a stack trace. Both the existing miscdev kunit suite + * (miscdev_test_duplicate_name) and any caller racing on the same + * name would otherwise pollute dmesg on every -EEXIST. + */ + { + struct miscdevice *c; + + list_for_each_entry(c, &misc_list, list) { + if (strcmp(c->name, misc->name) == 0) { + misc_minor_free(misc->minor); + if (is_dynamic) + misc->minor = MISC_DYNAMIC_MINOR; + err = -EEXIST; + goto out; + } + } + } + dev = MKDEV(MISC_MAJOR, misc->minor); misc->this_device = -- 2.34.1
