Commit 9912bbf6 authored Jun 20, 2018 by Qu Wenruo Committed by David Sterba Aug 06, 2018

btrfs: check-integrity: Fix NULL pointer dereference for degraded mount



Commit f8f84b2d ("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: f8f84b2d ("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>

parent 43a7e99d

fs/btrfs/check-integrity.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -1539,7 +1539,12 @@ static int btrfsic_map_block(struct btrfsic_state *state, u64 bytenr, u32 len,
		}

		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;

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