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| author |   Anton Eidelman <anton@lightbitslabs.com> | 2019-11-01 17:27:55 -0700 |
|---|---|---|
| committer |   Keith Busch <kbusch@kernel.org> | 2019-11-06 00:30:37 +0900 |
| commit | 763303a83a095a88c3a8a0d1abf97165db2e8bf5 (patch) | |
| tree | 0a9401afc0d1d0c2b23b8de4705a4ce49e2d8bea /drivers/nvme/host/multipath.c | |
| parent | nvme-rdma: fix a segmentation fault during module unload (diff) | |
| download | linux-dev-763303a83a095a88c3a8a0d1abf97165db2e8bf5.tar.xz linux-dev-763303a83a095a88c3a8a0d1abf97165db2e8bf5.zip | |
nvme-multipath: fix crash in nvme_mpath_clear_ctrl_paths
nvme_mpath_clear_ctrl_paths() iterates through
the ctrl->namespaces list while holding ctrl->scan_lock.
This does not seem to be the correct way of protecting
from concurrent list modification.
Specifically, nvme_scan_work() sorts ctrl->namespaces
AFTER unlocking scan_lock.
This may result in the following (rare) crash in ctrl disconnect
during scan_work:
BUG: kernel NULL pointer dereference, address: 0000000000000050
Oops: 0000 [#1] SMP PTI
CPU: 0 PID: 3995 Comm: nvme 5.3.5-050305-generic
RIP: 0010:nvme_mpath_clear_current_path+0xe/0x90 [nvme_core]
...
Call Trace:
nvme_mpath_clear_ctrl_paths+0x3c/0x70 [nvme_core]
nvme_remove_namespaces+0x35/0xe0 [nvme_core]
nvme_do_delete_ctrl+0x47/0x90 [nvme_core]
nvme_sysfs_delete+0x49/0x60 [nvme_core]
dev_attr_store+0x17/0x30
sysfs_kf_write+0x3e/0x50
kernfs_fop_write+0x11e/0x1a0
__vfs_write+0x1b/0x40
vfs_write+0xb9/0x1a0
ksys_write+0x67/0xe0
__x64_sys_write+0x1a/0x20
do_syscall_64+0x5a/0x130
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f8d02bfb154
Fix:
After taking scan_lock in nvme_mpath_clear_ctrl_paths()
down_read(&ctrl->namespaces_rwsem) as well to make list traversal safe.
This will not cause deadlocks because taking scan_lock never happens
while holding the namespaces_rwsem.
Moreover, scan work downs namespaces_rwsem in the same order.
Alternative: sort ctrl->namespaces in nvme_scan_work()
while still holding the scan_lock.
This would leave nvme_mpath_clear_ctrl_paths() without correct protection
against ctrl->namespaces modification by anyone other than scan_work.
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Diffstat (limited to '')
| -rw-r--r-- | drivers/nvme/host/multipath.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index fc99a40c1ec4..e0f064dcbd02 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -158,9 +158,11 @@ void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl) struct nvme_ns *ns; mutex_lock(&ctrl->scan_lock); + down_read(&ctrl->namespaces_rwsem); list_for_each_entry(ns, &ctrl->namespaces, list) if (nvme_mpath_clear_current_path(ns)) kblockd_schedule_work(&ns->head->requeue_work); + up_read(&ctrl->namespaces_rwsem); mutex_unlock(&ctrl->scan_lock); } |