diff options
| author | Tetsuo Handa | 2021-08-25 18:31:05 +0200 |
|---|---|---|
| committer | Jens Axboe | 2021-08-25 14:20:22 -0600 |
| commit | 75b7f62aa65d5c496391ec2c3db3561aaf81a403 (patch) | |
| tree | a930de7bca8bc3176fbd5b7537a7e8b75f81c4eb /drivers/block | |
| parent | 409e0ff10ead30a620ee48acb6d4545d9cb95359 (diff) | |
nbd: prevent IDR lookups from finding partially initialized devices
Previously nbd_index_mutex was held during whole add/remove/lookup
operations in order to guarantee that partially initialized devices are
not reachable via idr_find() or idr_for_each(). But now that partially
initialized devices become reachable as soon as idr_alloc() succeeds,
we need to skip partially initialized devices. Since it seems that
all functions use refcount_inc_not_zero(&nbd->refs) in order to skip
destroying devices, update nbd->refs from zero to non-zero as the last
step of device initialization in order to also skip partially initialized
devices.
Fixes: 6e4df4c64881 ("nbd: reduce the nbd_index_mutex scope")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
[hch: split from a larger patch, added comments]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210825163108.50713-4-hch@lst.de
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/block')
| -rw-r--r-- | drivers/block/nbd.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 938ca7f5a11f..b1ed2360ef32 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1747,7 +1747,11 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) mutex_init(&nbd->config_lock); refcount_set(&nbd->config_refs, 0); - refcount_set(&nbd->refs, refs); + /* + * Start out with a zero references to keep other threads from using + * this device until it is fully initialized. + */ + refcount_set(&nbd->refs, 0); INIT_LIST_HEAD(&nbd->list); disk->major = NBD_MAJOR; @@ -1766,6 +1770,11 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) disk->private_data = nbd; sprintf(disk->disk_name, "nbd%d", index); add_disk(disk); + + /* + * Now publish the device. + */ + refcount_set(&nbd->refs, refs); nbd_total_devices++; return nbd; |