On attempt to register a dynamic minor misc device its minor number is updated to a virtual minor number prior to device_create() call, however on error path misc->minor == MISC_DYNAMIC_MINOR is not restored.
Following the rule of thumb that a function returning an error must not change the state of the caller, assign MISC_DYNAMIC_MINOR back. The problem is met in a sutuation, when subsys_initcall(misc_init) is not yet called and misc_class is not created, but misc_register() modifies statically defined ".minor = MISC_DYNAMIC_MINOR", therefore implicitly changing the client's logic on next attempt (e.g. retrying from deferred list) to register a misc device, whose minor number is converted from dynamic to some unknown static one. Signed-off-by: Vladimir Zapolskiy <[email protected]> --- drivers/char/misc.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/drivers/char/misc.c b/drivers/char/misc.c index 9fd5a91..5113409 100644 --- a/drivers/char/misc.c +++ b/drivers/char/misc.c @@ -186,12 +186,13 @@ int misc_register(struct miscdevice * misc) { dev_t dev; int err = 0; + bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR); INIT_LIST_HEAD(&misc->list); mutex_lock(&misc_mtx); - if (misc->minor == MISC_DYNAMIC_MINOR) { + if (is_dynamic) { int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS); if (i >= DYNAMIC_MINORS) { err = -EBUSY; @@ -216,9 +217,13 @@ int misc_register(struct miscdevice * misc) device_create_with_groups(misc_class, misc->parent, dev, misc, misc->groups, "%s", misc->name); if (IS_ERR(misc->this_device)) { - int i = DYNAMIC_MINORS - misc->minor - 1; - if (i < DYNAMIC_MINORS && i >= 0) - clear_bit(i, misc_minors); + if (is_dynamic) { + int i = DYNAMIC_MINORS - misc->minor - 1; + + if (i < DYNAMIC_MINORS && i >= 0) + clear_bit(i, misc_minors); + misc->minor = MISC_DYNAMIC_MINOR; + } err = PTR_ERR(misc->this_device); goto out; } -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
