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Commit 54561783 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

lockdep: in_range() fix 



Torsten Kaiser wrote:

| static inline int in_range(const void *start, const void *addr, const void *end)
| {
|         return addr >= start && addr <= end;
| }
| This  will return true, if addr is in the range of start (including)
| to end (including).
|
| But debug_check_no_locks_freed() seems does:
| const void *mem_to = mem_from + mem_len
| -> mem_to is the last byte of the freed range, that fits in_range
| lock_from = (void *)hlock->instance;
| -> first byte of the lock
| lock_to = (void *)(hlock->instance + 1);
| -> first byte of the next lock, not last byte of the lock that is being checked!
|
| The test is:
| if (!in_range(mem_from, lock_from, mem_to) &&
|                                         !in_range(mem_from, lock_to, mem_to))
|                         continue;
| So it tests, if the first byte of the lock is in the range that is freed ->OK
| And if the first byte of the *next* lock is in the range that is freed
| -> Not OK.

We can also simplify in_range checks, we need only 2 comparisons, not 4.
If the lock is not in memory range, it should be either at the left of range
or at the right.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
parent 85684873

kernel/lockdep.c

+10 −12
Original line number Diff line number Diff line
@@ -3054,11 +3054,6 @@ void __init lockdep_info(void) 
#endif

}



static inline int in_range(const void *start, const void *addr, const void *end)

{

	return addr >= start && addr <= end;

}



static void

print_freed_lock_bug(struct task_struct *curr, const void *mem_from,

		     const void *mem_to, struct held_lock *hlock)
@@ -3080,6 +3075,13 @@ print_freed_lock_bug(struct task_struct *curr, const void *mem_from, 
	dump_stack();

}



static inline int not_in_range(const void* mem_from, unsigned long mem_len,

				const void* lock_from, unsigned long lock_len)

{

	return lock_from + lock_len <= mem_from ||

		mem_from + mem_len <= lock_from;

}



/*

 * Called when kernel memory is freed (or unmapped), or if a lock

 * is destroyed or reinitialized - this code checks whether there is
@@ -3087,7 +3089,6 @@ print_freed_lock_bug(struct task_struct *curr, const void *mem_from, 
 */

void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)

{

	const void *mem_to = mem_from + mem_len, *lock_from, *lock_to;

	struct task_struct *curr = current;

	struct held_lock *hlock;

	unsigned long flags;
@@ -3100,14 +3101,11 @@ void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len) 
	for (i = 0; i < curr->lockdep_depth; i++) {

		hlock = curr->held_locks + i;



		lock_from = (void *)hlock->instance;

		lock_to = (void *)(hlock->instance + 1);



		if (!in_range(mem_from, lock_from, mem_to) &&

					!in_range(mem_from, lock_to, mem_to))

		if (not_in_range(mem_from, mem_len, hlock->instance,

					sizeof(*hlock->instance)))

			continue;



		print_freed_lock_bug(curr, mem_from, mem_to, hlock);

		print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);

		break;

	}

	local_irq_restore(flags);