char: misc: restore MISC_DYNAMIC_MINOR on device_create() failure
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 <vladimir_zapolskiy@mentor.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>hifive-unleashed-5.1
parent
b144ce2d37
commit
b575f7124a
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@ -186,12 +186,13 @@ int misc_register(struct miscdevice * misc)
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{
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{
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dev_t dev;
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dev_t dev;
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int err = 0;
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int err = 0;
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bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
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INIT_LIST_HEAD(&misc->list);
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INIT_LIST_HEAD(&misc->list);
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mutex_lock(&misc_mtx);
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mutex_lock(&misc_mtx);
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if (misc->minor == MISC_DYNAMIC_MINOR) {
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if (is_dynamic) {
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int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
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int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
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if (i >= DYNAMIC_MINORS) {
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if (i >= DYNAMIC_MINORS) {
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err = -EBUSY;
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err = -EBUSY;
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@ -216,9 +217,13 @@ int misc_register(struct miscdevice * misc)
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device_create_with_groups(misc_class, misc->parent, dev,
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device_create_with_groups(misc_class, misc->parent, dev,
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misc, misc->groups, "%s", misc->name);
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misc, misc->groups, "%s", misc->name);
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if (IS_ERR(misc->this_device)) {
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if (IS_ERR(misc->this_device)) {
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int i = DYNAMIC_MINORS - misc->minor - 1;
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if (is_dynamic) {
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if (i < DYNAMIC_MINORS && i >= 0)
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int i = DYNAMIC_MINORS - misc->minor - 1;
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clear_bit(i, misc_minors);
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if (i < DYNAMIC_MINORS && i >= 0)
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clear_bit(i, misc_minors);
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misc->minor = MISC_DYNAMIC_MINOR;
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}
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err = PTR_ERR(misc->this_device);
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err = PTR_ERR(misc->this_device);
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goto out;
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goto out;
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}
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}
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