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 <[email protected]>
---
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
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 <[email protected]>
> ---
> 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 <[email protected]>
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
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 <[email protected]>
---
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
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 <[email protected]>
Looks good.
Reviewed-by: Ralph Campbell <[email protected]>