lkml.org 
[lkml]   [2020]   [Sep]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] mm/hmm/test: use after free in dmirror_allocate_chunk()
From
Date

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>

\
 
 \ /
  Last update: 2020-09-22 19:32    [W:0.048 / U:0.328 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site