[PATCH] libnvdimm/pmem: Fix blk_cleanup_disk() usage

[Dan Williams]

The queue_to_disk() helper can not be used after del_gendisk()
communicate @disk via the pgmap->owner.

Reported-by: Sachin Sant <***@linux.vnet.ibm.com>
Fixes: 87eb73b2ca7c ("nvdimm-pmem: convert to blk_alloc_disk/blk_cleanup_disk")
Cc: Christoph Hellwig <***@lst.de>
Cc: Ulf Hansson <***@linaro.org>
Cc: Jens Axboe <***@kernel.dk>
Signed-off-by: Dan Williams <***@intel.com>
---
Jens,

Please take or fold this into your tree after Sachin has a chance
to test it out. It's passing my tests.

drivers/nvdimm/pmem.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 31f3c4bd6f72..fc6b78dd2d24 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -337,8 +337,9 @@ static void pmem_pagemap_cleanup(struct dev_pagemap *pgmap)
{
struct request_queue *q =
container_of(pgmap->ref, struct request_queue, q_usage_counter);
+ struct pmem_device *pmem = pgmap->owner;

- blk_cleanup_disk(queue_to_disk(q));
+ blk_cleanup_disk(pmem->disk);
}

static void pmem_release_queue(void *pgmap)
@@ -427,6 +428,7 @@ static int pmem_attach_disk(struct device *dev,
q = disk->queue;

pmem->disk = disk;
+ pmem->pgmap.owner = pmem;
pmem->pfn_flags = PFN_DEV;
pmem->pgmap.ref = &q->q_usage_counter;
if (is_nd_pfn(dev)) {

[Dan Williams]

The queue_to_disk() helper can not be used after del_gendisk()
communicate @disk via the pgmap->owner.

Otherwise, queue_to_disk() returns NULL resulting in the splat below.

Kernel attempted to read user page (330) - exploit attempt? (uid: 0)
BUG: Kernel NULL pointer dereference on read at 0x00000330
Faulting instruction address: 0xc000000000906344
Oops: Kernel access of bad area, sig: 11 [#1]
[..]
NIP [c000000000906344] pmem_pagemap_cleanup+0x24/0x40
LR [c0000000004701d4] memunmap_pages+0x1b4/0x4b0
Call Trace:
[c000000022cbb9c0] [c0000000009063c8] pmem_pagemap_kill+0x28/0x40 (unreliable)
[c000000022cbb9e0] [c0000000004701d4] memunmap_pages+0x1b4/0x4b0
[c000000022cbba90] [c0000000008b28a0] devm_action_release+0x30/0x50
[c000000022cbbab0] [c0000000008b39c8] release_nodes+0x2f8/0x3e0
[c000000022cbbb60] [c0000000008ac440] device_release_driver_internal+0x190/0x2b0
[c000000022cbbba0] [c0000000008a8450] unbind_store+0x130/0x170

Reported-by: Sachin Sant <***@linux.vnet.ibm.com>
Fixes: 87eb73b2ca7c ("nvdimm-pmem: convert to blk_alloc_disk/blk_cleanup_disk")
Link: http://lore.kernel.org/r/DFB75BA8-603F-4A35-880B-***@linux.vnet.ibm.com
Cc: Christoph Hellwig <***@lst.de>
Cc: Ulf Hansson <***@linaro.org>
Cc: Jens Axboe <***@kernel.dk>
Signed-off-by: Dan Williams <***@intel.com>
---
Changes in v2 Improve the changelog.

drivers/nvdimm/pmem.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 31f3c4bd6f72..fc6b78dd2d24 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -337,8 +337,9 @@ static void pmem_pagemap_cleanup(struct dev_pagemap *pgmap)
{
struct request_queue *q =
container_of(pgmap->ref, struct request_queue, q_usage_counter);
+ struct pmem_device *pmem = pgmap->owner;

- blk_cleanup_disk(queue_to_disk(q));
+ blk_cleanup_disk(pmem->disk);
}

static void pmem_release_queue(void *pgmap)
@@ -427,6 +428,7 @@ static int pmem_attach_disk(struct device *dev,
q = disk->queue;

pmem->disk = disk;
+ pmem->pgmap.owner = pmem;
pmem->pfn_flags = PFN_DEV;
pmem->pgmap.ref = &q->q_usage_counter;
if (is_nd_pfn(dev)) {

[Christoph Hellwig]

Thanks Dan, this looks good to me:

Reviewed-by: Christoph Hellwig <***@lst.de>

Jens, can you quickly pick this up?

[Sachin Sant]

Post by Dan Williams
Fixes: 87eb73b2ca7c ("nvdimm-pmem: convert to blk_alloc_disk/blk_cleanup_disk")
---

Thanks Dan. This patch fixes the reported crash for me.

Post by Dan Williams
Changes in v2 Improve the changelog.
drivers/nvdimm/pmem.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 31f3c4bd6f72..fc6b78dd2d24 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -337,8 +337,9 @@ static void pmem_pagemap_cleanup(struct dev_pagemap *pgmap)
{
struct request_queue *q =
container_of(pgmap->ref, struct request_queue, q_usage_counter);

With this change variable ‘q' is no longer needed and can be removed.

drivers/nvdimm/pmem.c: In function 'pmem_pagemap_cleanup':
drivers/nvdimm/pmem.c:338:24: warning: unused variable 'q' [-Wunused-variable]
struct request_queue *q =
^

Post by Dan Williams
+ struct pmem_device *pmem = pgmap->owner;
- blk_cleanup_disk(queue_to_disk(q));
+ blk_cleanup_disk(pmem->disk);
}
static void pmem_release_queue(void *pgmap)
@@ -427,6 +428,7 @@ static int pmem_attach_disk(struct device *dev,
q = disk->queue;
pmem->disk = disk;
+ pmem->pgmap.owner = pmem;
pmem->pfn_flags = PFN_DEV;
pmem->pgmap.ref = &q->q_usage_counter;
if (is_nd_pfn(dev)) {

Thanks
-Sachin