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Commit 10db4ef7 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86, PEBS/DS: fix code flow in ds_request() 



this compiler warning:

  arch/x86/kernel/ds.c: In function 'ds_request':
  arch/x86/kernel/ds.c:368: warning: 'context' may be used uninitialized in this function

Shows that the code flow in ds_request() is buggy - it goes into
the unlock+release-context path even when the context is not allocated
yet.

First allocate the context, then do the other checks.

Also, take care with GFP allocations under the ds_lock spinlock.

Cc: <stable@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 93ce99e8

arch/x86/kernel/ds.c

+21 −5
Original line number Diff line number Diff line
@@ -236,17 +236,33 @@ static inline struct ds_context *ds_alloc_context(struct task_struct *task) 
	struct ds_context *context = *p_context;



	if (!context) {

		spin_unlock(&ds_lock);



		context = kzalloc(sizeof(*context), GFP_KERNEL);



		if (!context)

		if (!context) {

			spin_lock(&ds_lock);

			return NULL;

		}



		context->ds = kzalloc(ds_cfg.sizeof_ds, GFP_KERNEL);

		if (!context->ds) {

			kfree(context);

			spin_lock(&ds_lock);

			return NULL;

		}



		spin_lock(&ds_lock);

		/*

		 * Check for race - another CPU could have allocated

		 * it meanwhile:

		 */

		if (*p_context) {

			kfree(context->ds);

			kfree(context);

			return *p_context;

		}



		*p_context = context;



		context->this = p_context;
@@ -384,15 +400,15 @@ static int ds_request(struct task_struct *task, void *base, size_t size, 


	spin_lock(&ds_lock);



	error = -EPERM;

	if (!check_tracer(task))

		goto out_unlock;



	error = -ENOMEM;

	context = ds_alloc_context(task);

	if (!context)

		goto out_unlock;



	error = -EPERM;

	if (!check_tracer(task))

		goto out_unlock;



	error = -EALREADY;

	if (context->owner[qual] == current)

		goto out_unlock;