[PATCH] mm/hmm/test: use after free in dmirror_allocate_chunk()

[PATCH] mm/hmm/test: use after free in dmirror_allocate_chunk()

[Dan Carpenter]

The error handling code does this:

err_free:
	kfree(devmem);
        ^^^^^^^^^^^^^
err_release:
	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
                           ^^^^^^^^
The problem is that when we use "devmem->pagemap.range.start" the
"devmem" pointer is either NULL or freed.

Neither the allocation nor the call to request_free_mem_region() has to
be done under the lock so I moved those to the start of the function.

Fixes: b2ef9f5a5cb3 ("mm/hmm/test: add selftest driver for HMM")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
It's weird that I didn't catch the use after free when this code was
merged in May...  My bad.  Not sure what happened there.  How I found
this was that I have been reviewing release_mem_region() leaks and the
NULL dereference path is a leak.


 lib/test_hmm.c | 47 ++++++++++++++++++++++++-----------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index c8133f50160b..0503c78cb322 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -459,6 +459,22 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 	unsigned long pfn_last;
 	void *ptr;
 
+	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
+	if (!devmem)
+		return -ENOMEM;
+
+	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
+				      "hmm_dmirror");
+	if (IS_ERR(res))
+		goto err_devmem;
+
+	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
+	devmem->pagemap.range.start = res->start;
+	devmem->pagemap.range.end = res->end;
+	devmem->pagemap.nr_range = 1;
+	devmem->pagemap.ops = &dmirror_devmem_ops;
+	devmem->pagemap.owner = mdevice;
+
 	mutex_lock(&mdevice->devmem_lock);
 
 	if (mdevice->devmem_count == mdevice->devmem_capacity) {
@@ -471,30 +487,16 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 				sizeof(new_chunks[0]) * new_capacity,
 				GFP_KERNEL);
 		if (!new_chunks)
-			goto err;
+			goto err_release;
 		mdevice->devmem_capacity = new_capacity;
 		mdevice->devmem_chunks = new_chunks;
 	}
 
-	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
-					"hmm_dmirror");
-	if (IS_ERR(res))
-		goto err;
-
-	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
-	if (!devmem)
-		goto err_release;
-
-	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
-	devmem->pagemap.range.start = res->start;
-	devmem->pagemap.range.end = res->end;
-	devmem->pagemap.nr_range = 1;
-	devmem->pagemap.ops = &dmirror_devmem_ops;
-	devmem->pagemap.owner = mdevice;
-
 	ptr = memremap_pages(&devmem->pagemap, numa_node_id());
-	if (IS_ERR(ptr))
-		goto err_free;
+	if (IS_ERR(ptr)) {
+		mutex_unlock(&mdevice->devmem_lock);
+		goto err_release;
+	}
 
 	devmem->mdevice = mdevice;
 	pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT;
@@ -525,12 +527,11 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 
 	return true;
 
-err_free:
-	kfree(devmem);
 err_release:
 	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
-err:
-	mutex_unlock(&mdevice->devmem_lock);
+err_devmem:
+	kfree(devmem);
+
 	return false;
 }
 
-- 
2.28.0

Re: [PATCH] mm/hmm/test: use after free in dmirror_allocate_chunk()

[Ralph Campbell]

On 9/22/20 1:12 AM, Dan Carpenter wrote:
> The error handling code does this:
> 
> err_free:
> 	kfree(devmem);
>          ^^^^^^^^^^^^^
> err_release:
> 	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
>                             ^^^^^^^^
> The problem is that when we use "devmem->pagemap.range.start" the
> "devmem" pointer is either NULL or freed.
> 
> Neither the allocation nor the call to request_free_mem_region() has to
> be done under the lock so I moved those to the start of the function.
> 
> Fixes: b2ef9f5a5cb3 ("mm/hmm/test: add selftest driver for HMM")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> It's weird that I didn't catch the use after free when this code was
> merged in May...  My bad.  Not sure what happened there.  How I found
> this was that I have been reviewing release_mem_region() leaks and the
> NULL dereference path is a leak.
> 

Thanks for fixing this. I missed it too. :-)

>   lib/test_hmm.c | 47 ++++++++++++++++++++++++-----------------------
>   1 file changed, 24 insertions(+), 23 deletions(-)
> 
> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> index c8133f50160b..0503c78cb322 100644
> --- a/lib/test_hmm.c
> +++ b/lib/test_hmm.c
> @@ -459,6 +459,22 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
>   	unsigned long pfn_last;
>   	void *ptr;
>   
> +	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
> +	if (!devmem)
> +		return -ENOMEM;
> +
> +	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
> +				      "hmm_dmirror");
> +	if (IS_ERR(res))
> +		goto err_devmem;
> +
> +	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
> +	devmem->pagemap.range.start = res->start;
> +	devmem->pagemap.range.end = res->end;
> +	devmem->pagemap.nr_range = 1;
> +	devmem->pagemap.ops = &dmirror_devmem_ops;
> +	devmem->pagemap.owner = mdevice;
> +
>   	mutex_lock(&mdevice->devmem_lock);
>   
>   	if (mdevice->devmem_count == mdevice->devmem_capacity) {
> @@ -471,30 +487,16 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
>   				sizeof(new_chunks[0]) * new_capacity,
>   				GFP_KERNEL);
>   		if (!new_chunks)

Need to call mutex_unlock(&mdevice->devmem_lock).
In fact, why not make this goto err_unlock and add
err_unlock: mutex_unlock() before the err_release:.

> -			goto err;
> +			goto err_release;>   		mdevice->devmem_capacity = new_capacity;
>   		mdevice->devmem_chunks = new_chunks;
>   	}
>   
> -	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
> -					"hmm_dmirror");
> -	if (IS_ERR(res))
> -		goto err;
> -
> -	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
> -	if (!devmem)
> -		goto err_release;
> -
> -	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
> -	devmem->pagemap.range.start = res->start;
> -	devmem->pagemap.range.end = res->end;
> -	devmem->pagemap.nr_range = 1;
> -	devmem->pagemap.ops = &dmirror_devmem_ops;
> -	devmem->pagemap.owner = mdevice;
> -
>   	ptr = memremap_pages(&devmem->pagemap, numa_node_id());
> -	if (IS_ERR(ptr))
> -		goto err_free;
> +	if (IS_ERR(ptr)) {
> +		mutex_unlock(&mdevice->devmem_lock);
> +		goto err_release;
> +	}

This could then be just goto err_unlock.

>   	devmem->mdevice = mdevice;
>   	pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT;
> @@ -525,12 +527,11 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
>   
>   	return true;
>   
> -err_free:
> -	kfree(devmem);
>   err_release:
>   	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
> -err:
> -	mutex_unlock(&mdevice->devmem_lock);
> +err_devmem:
> +	kfree(devmem);
> +
>   	return false;
>   }
>   

With the suggested change, you can add
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>

[PATCH v2] mm/hmm/test: use after free in dmirror_allocate_chunk()

[Dan Carpenter]

The error handling code does this:

err_free:
	kfree(devmem);
        ^^^^^^^^^^^^^
err_release:
	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
                           ^^^^^^^^
The problem is that when we use "devmem->pagemap.range.start" the
"devmem" pointer is either NULL or freed.

Neither the allocation nor the call to request_free_mem_region() has to
be done under the lock so I moved those to the start of the function.

Fixes: b2ef9f5a5cb3 ("mm/hmm/test: add selftest driver for HMM")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2:  The first version introduced a locking bug

 lib/test_hmm.c | 44 ++++++++++++++++++++++----------------------
 1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index c8133f50160b..e151a7f10519 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -459,6 +459,22 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 	unsigned long pfn_last;
 	void *ptr;
 
+	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
+	if (!devmem)
+		return -ENOMEM;
+
+	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
+				      "hmm_dmirror");
+	if (IS_ERR(res))
+		goto err_devmem;
+
+	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
+	devmem->pagemap.range.start = res->start;
+	devmem->pagemap.range.end = res->end;
+	devmem->pagemap.nr_range = 1;
+	devmem->pagemap.ops = &dmirror_devmem_ops;
+	devmem->pagemap.owner = mdevice;
+
 	mutex_lock(&mdevice->devmem_lock);
 
 	if (mdevice->devmem_count == mdevice->devmem_capacity) {
@@ -471,30 +487,14 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 				sizeof(new_chunks[0]) * new_capacity,
 				GFP_KERNEL);
 		if (!new_chunks)
-			goto err;
+			goto err_release;
 		mdevice->devmem_capacity = new_capacity;
 		mdevice->devmem_chunks = new_chunks;
 	}
 
-	res = request_free_mem_region(&iomem_resource, DEVMEM_CHUNK_SIZE,
-					"hmm_dmirror");
-	if (IS_ERR(res))
-		goto err;
-
-	devmem = kzalloc(sizeof(*devmem), GFP_KERNEL);
-	if (!devmem)
-		goto err_release;
-
-	devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
-	devmem->pagemap.range.start = res->start;
-	devmem->pagemap.range.end = res->end;
-	devmem->pagemap.nr_range = 1;
-	devmem->pagemap.ops = &dmirror_devmem_ops;
-	devmem->pagemap.owner = mdevice;
-
 	ptr = memremap_pages(&devmem->pagemap, numa_node_id());
 	if (IS_ERR(ptr))
-		goto err_free;
+		goto err_release;
 
 	devmem->mdevice = mdevice;
 	pfn_first = devmem->pagemap.range.start >> PAGE_SHIFT;
@@ -525,12 +525,12 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
 
 	return true;
 
-err_free:
-	kfree(devmem);
 err_release:
-	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
-err:
 	mutex_unlock(&mdevice->devmem_lock);
+	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
+err_devmem:
+	kfree(devmem);
+
 	return false;
 }
 
-- 
2.28.0

Re: [PATCH] mm/hmm/test: use after free in dmirror_allocate_chunk()

[Dan Carpenter]

On Tue, Sep 22, 2020 at 10:31:01AM -0700, Ralph Campbell wrote:
> > @@ -471,30 +487,16 @@ static bool dmirror_allocate_chunk(struct dmirror_device *mdevice,
> >   				sizeof(new_chunks[0]) * new_capacity,
> >   				GFP_KERNEL);
> >   		if (!new_chunks)
> 
> Need to call mutex_unlock(&mdevice->devmem_lock).
> In fact, why not make this goto err_unlock and add
> err_unlock: mutex_unlock() before the err_release:.

Ugh...  Thanks for catching that.

regards,
dan carpenter

Re: [PATCH v2] mm/hmm/test: use after free in dmirror_allocate_chunk()

[Ralph Campbell]

On 9/24/20 6:46 AM, Dan Carpenter wrote:
> The error handling code does this:
> 
> err_free:
> 	kfree(devmem);
>          ^^^^^^^^^^^^^
> err_release:
> 	release_mem_region(devmem->pagemap.range.start, range_len(&devmem->pagemap.range));
>                             ^^^^^^^^
> The problem is that when we use "devmem->pagemap.range.start" the
> "devmem" pointer is either NULL or freed.
> 
> Neither the allocation nor the call to request_free_mem_region() has to
> be done under the lock so I moved those to the start of the function.
> 
> Fixes: b2ef9f5a5cb3 ("mm/hmm/test: add selftest driver for HMM")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Looks good.
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>