Messages in this thread | | | Subject | Re: [PATCH] mm/hmm/test: use after free in dmirror_allocate_chunk() | From | Ralph Campbell <> | Date | Tue, 22 Sep 2020 10:31:01 -0700 |
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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>
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