Holding the reconfig_mutex over a potential userspace fault sets up a
lockdep dependency chain between filesystem-DAX and the libnvdimm ioctl
path. Move the user access outside of the lock.
[ INFO: possible circular locking dependency detected ]
4.11.0-rc3+ #13 Tainted: G W O
-------------------------------------------------------
fallocate/16656 is trying to acquire lock:
(&nvdimm_bus->reconfig_mutex){+.+.+.}, at: [<ffffffffa00080b1>] nvdimm_bus_lock+0x21/0x30 [libnvdimm]
but task is already holding lock:
(jbd2_handle){++++..}, at: [<ffffffff813b4944>] start_this_handle+0x104/0x460
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (jbd2_handle){++++..}:
lock_acquire+0xbd/0x200
start_this_handle+0x16a/0x460
jbd2__journal_start+0xe9/0x2d0
__ext4_journal_start_sb+0x89/0x1c0
ext4_dirty_inode+0x32/0x70
__mark_inode_dirty+0x235/0x670
generic_update_time+0x87/0xd0
touch_atime+0xa9/0xd0
ext4_file_mmap+0x90/0xb0
mmap_region+0x370/0x5b0
do_mmap+0x415/0x4f0
vm_mmap_pgoff+0xd7/0x120
SyS_mmap_pgoff+0x1c5/0x290
SyS_mmap+0x22/0x30
entry_SYSCALL_64_fastpath+0x1f/0xc2
-> #1 (&mm->mmap_sem){++++++}:
lock_acquire+0xbd/0x200
__might_fault+0x70/0xa0
__nd_ioctl+0x683/0x720 [libnvdimm]
nvdimm_ioctl+0x8b/0xe0 [libnvdimm]
do_vfs_ioctl+0xa8/0x740
SyS_ioctl+0x79/0x90
do_syscall_64+0x6c/0x200
return_from_SYSCALL_64+0x0/0x7a
-> #0 (&nvdimm_bus->reconfig_mutex){+.+.+.}:
__lock_acquire+0x16b6/0x1730
lock_acquire+0xbd/0x200
__mutex_lock+0x88/0x9b0
mutex_lock_nested+0x1b/0x20
nvdimm_bus_lock+0x21/0x30 [libnvdimm]
nvdimm_forget_poison+0x25/0x50 [libnvdimm]
nvdimm_clear_poison+0x106/0x140 [libnvdimm]
pmem_do_bvec+0x1c2/0x2b0 [nd_pmem]
pmem_make_request+0xf9/0x270 [nd_pmem]
generic_make_request+0x118/0x3b0
submit_bio+0x75/0x150
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 62232e45f4a2 ("libnvdimm: control (ioctl) messages for nvdimm_bus and nvdimm devices")
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Reported-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
drivers/nvdimm/bus.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index 23d4a1728cdf..351bac8f6503 100644
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -934,8 +934,14 @@ static int __nd_ioctl(struct nvdimm_bus *nvdimm_bus, struct nvdimm *nvdimm,
rc = nd_desc->ndctl(nd_desc, nvdimm, cmd, buf, buf_len, NULL);
if (rc < 0)
goto out_unlock;
+ nvdimm_bus_unlock(&nvdimm_bus->dev);
+
if (copy_to_user(p, buf, buf_len))
rc = -EFAULT;
+
+ vfree(buf);
+ return rc;
+
out_unlock:
nvdimm_bus_unlock(&nvdimm_bus->dev);
out: