| Message ID | 20200926121402.GA7467@kadam (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] mm/hmm/test: use after free in dmirror_allocate_chunk() | expand |
> One problem with the kernel QC process is that I think everyone marks > the bug as "old/dealt with" Will this view trigger any more clarifications? > so it was only because I was added a new > check for resource leaks that it was found when it was re-introduced. I would like to point once more out that the commit 786ae133e07f2a6b352a0efad16b555ee45a2898 ("lib: fix test_hmm.c reference after free" from 2020-06-26) indicated questionable implementation details according to a coccicheck run. The available scripts for the semantic patch language can also remind you again for desirable software improvements. Examples: * https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/coccinelle/free/kfree.cocci?id=7c7ec3226f5f33f9c050d85ec20f18419c622ad6#n2 * https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/scripts/coccinelle/null/deref_null.cocci?id=7c7ec3226f5f33f9c050d85ec20f18419c622ad6#n3 Will any more adjustments be achieved with the help of advanced source code analysis tools? Regards, Markus
On Sat, Sep 26, 2020 at 03:14:02PM +0300, 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: 1f9c4bb986d9 ("mm/memremap_pages: convert to 'struct range'") > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > Reviewed-by: Ralph Campbell <rcampbell@nvidia.com> > --- > v2: The first version introduced a locking bug > v3: Markus Elfring pointed out that the Fixes tag was wrong. This bug > was in the original commit and then fixed and then re-introduced. I was > quite bothered by how this bug lasted so long in the source code, but > now we know. As soon as it is introduced we fixed it. > > One problem with the kernel QC process is that I think everyone marks > the bug as "old/dealt with" so it was only because I was added a new > check for resource leaks that it was found when it was re-introduced. > > lib/test_hmm.c | 44 ++++++++++++++++++++++---------------------- > 1 file changed, 22 insertions(+), 22 deletions(-) Hi Andrew, I don't have have any hmm related patches this cycle, can you take this into your tree? Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Thanks, Jason
On Sat, 26 Sep 2020 19:17:20 -0300 Jason Gunthorpe <jgg@ziepe.ca> wrote: > On Sat, Sep 26, 2020 at 03:14:02PM +0300, 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: 1f9c4bb986d9 ("mm/memremap_pages: convert to 'struct range'") > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > > Reviewed-by: Ralph Campbell <rcampbell@nvidia.com> > > --- > > v2: The first version introduced a locking bug > > v3: Markus Elfring pointed out that the Fixes tag was wrong. This bug > > was in the original commit and then fixed and then re-introduced. I was > > quite bothered by how this bug lasted so long in the source code, but > > now we know. As soon as it is introduced we fixed it. > > > > One problem with the kernel QC process is that I think everyone marks > > the bug as "old/dealt with" so it was only because I was added a new > > check for resource leaks that it was found when it was re-introduced. > > > > lib/test_hmm.c | 44 ++++++++++++++++++++++---------------------- > > 1 file changed, 22 insertions(+), 22 deletions(-) > > Hi Andrew, > > I don't have have any hmm related patches this cycle, can you take > this into your tree? > > Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Thanks. It's actually a fix against Dan Williams' -mm patch "mm/memremap_pages: convert to 'struct range'"
On Mon, Sep 28, 2020 at 5:52 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Sat, 26 Sep 2020 19:17:20 -0300 Jason Gunthorpe <jgg@ziepe.ca> wrote: > > > On Sat, Sep 26, 2020 at 03:14:02PM +0300, 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: 1f9c4bb986d9 ("mm/memremap_pages: convert to 'struct range'") > > > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> > > > Reviewed-by: Ralph Campbell <rcampbell@nvidia.com> > > > --- > > > v2: The first version introduced a locking bug > > > v3: Markus Elfring pointed out that the Fixes tag was wrong. This bug > > > was in the original commit and then fixed and then re-introduced. I was > > > quite bothered by how this bug lasted so long in the source code, but > > > now we know. As soon as it is introduced we fixed it. > > > > > > One problem with the kernel QC process is that I think everyone marks > > > the bug as "old/dealt with" so it was only because I was added a new > > > check for resource leaks that it was found when it was re-introduced. > > > > > > lib/test_hmm.c | 44 ++++++++++++++++++++++---------------------- > > > 1 file changed, 22 insertions(+), 22 deletions(-) > > > > Hi Andrew, > > > > I don't have have any hmm related patches this cycle, can you take > > this into your tree? > > > > Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> > > Thanks. > > It's actually a fix against Dan Williams' -mm patch "mm/memremap_pages: > convert to 'struct range'" Yes, sorry, for the fix: Acked-by: Dan Williams <dan.j.williams@intel.com>
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; }
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: 1f9c4bb986d9 ("mm/memremap_pages: convert to 'struct range'") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Reviewed-by: Ralph Campbell <rcampbell@nvidia.com> --- v2: The first version introduced a locking bug v3: Markus Elfring pointed out that the Fixes tag was wrong. This bug was in the original commit and then fixed and then re-introduced. I was quite bothered by how this bug lasted so long in the source code, but now we know. As soon as it is introduced we fixed it. One problem with the kernel QC process is that I think everyone marks the bug as "old/dealt with" so it was only because I was added a new check for resource leaks that it was found when it was re-introduced. lib/test_hmm.c | 44 ++++++++++++++++++++++---------------------- 1 file changed, 22 insertions(+), 22 deletions(-)