4.18-stable review patch. If anyone has any objections, please let me know.
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From: Qu Wenruo wqu@suse.com
[ Upstream commit 9912bbf6440ba0555e91d3306520da01872c7c1d ]
Commit f8f84b2dfda5 ("btrfs: index check-integrity state hash by a dev_t") changed how btrfsic indexes device state.
Now we need to access device->bdev->bd_dev, while for degraded mount it's completely possible to have device->bdev as NULL, thus it will trigger a NULL pointer dereference at mount time.
Fix it by checking if the device is degraded before accessing device->bdev->bd_dev.
There are a lot of other places accessing device->bdev->bd_dev, however the other call sites have either checked device->bdev, or the device->bdev is passed from btrfsic_map_block(), so it won't cause harm.
Fixes: f8f84b2dfda5 ("btrfs: index check-integrity state hash by a dev_t") Signed-off-by: Qu Wenruo wqu@suse.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/check-integrity.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
--- a/fs/btrfs/check-integrity.c +++ b/fs/btrfs/check-integrity.c @@ -1539,7 +1539,12 @@ static int btrfsic_map_block(struct btrf }
device = multi->stripes[0].dev; - block_ctx_out->dev = btrfsic_dev_state_lookup(device->bdev->bd_dev); + if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state) || + !device->bdev || !device->name) + block_ctx_out->dev = NULL; + else + block_ctx_out->dev = btrfsic_dev_state_lookup( + device->bdev->bd_dev); block_ctx_out->dev_bytenr = multi->stripes[0].physical; block_ctx_out->start = bytenr; block_ctx_out->len = len;