Messages in this thread | | | Date | Tue, 13 Oct 2009 17:52:07 +0000 | From | iceberg <> | Subject | [BUG] ati_remote2.c: possible mutex_lock without mutex_unlock |
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KERNEL_VERSION: 2.6.31 DESCRIBE:
In driver ./drivers/input/input.c possible call to mutex_lock from function input_devices_seq_start without mutex_unlock.
After calling input_devices_seq_start we can't know whether mutex was locked or not. Case 1. If mutex_lock_interruptible was not locked due to interrupt then input_devices_seq_start returns NULL. Case 2. If mutex was successfuly locked but seq_list_start returned NULL then input_devices_seq_start returns NULL too. The last case occurs if seq_list_start is called with pos>size of input_dev_list or pos<0.
Hence, after calling input_devices_seq_start we can not simply check that result is not NULL and call input_devices_seq_stop function which unlocks the mutex. Because in case 2 the mutex will stay locked. void * ret = input_devices_seq_start(...); if(ret!=NULL) { //mutex is acquired for sure input_devices_seq_stop(...);//unlocks the mutex } else { //mutex may be acquired or not }
783 static void *input_devices_seq_start(struct seq_file *seq, loff_t *pos) 784{ 785 if (mutex_lock_interruptible(&input_mutex)) 786 return NULL; 787 788 return seq_list_start(&input_dev_list, *pos); 789}
663struct list_head *seq_list_start(struct list_head *head, loff_t pos) 664{ 665 struct list_head *lh; 666 667 list_for_each(lh, head) 668 if (pos-- == 0) 669 return lh; 670 671 return NULL; 672} 673 674EXPORT_SYMBOL(seq_list_start); 675
Found by: Linux Driver Verification project
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