4.14-stable review patch. If anyone has any objections, please let me know.
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From: Anand Jain anand.jain@oracle.com
[ Upstream commit 801660b040d132f67fac6a95910ad307c5929b49 ]
Test case btrfs/164 reports use-after-free:
[ 6712.084324] general protection fault: 0000 [#1] PREEMPT SMP .. [ 6712.195423] btrfs_update_commit_device_size+0x75/0xf0 [btrfs] [ 6712.201424] btrfs_commit_transaction+0x57d/0xa90 [btrfs] [ 6712.206999] btrfs_rm_device+0x627/0x850 [btrfs] [ 6712.211800] btrfs_ioctl+0x2b03/0x3120 [btrfs]
Reason for this is that btrfs_shrink_device adds the resized device to the fs_devices::resized_devices after it has called the last commit transaction.
So the list fs_devices::resized_devices is not empty when btrfs_shrink_device returns. Now the parent function btrfs_rm_device calls:
btrfs_close_bdev(device); call_rcu(&device->rcu, free_device_rcu);
and then does the transactio ncommit. It goes through the fs_devices::resized_devices in btrfs_update_commit_device_size and leads to use-after-free.
Fix this by making sure btrfs_shrink_device calls the last needed btrfs_commit_transaction before the return. This is consistent with what the grow counterpart does and this makes sure the on-disk state is persistent when the function returns.
Reported-by: Lu Fengqi lufq.fnst@cn.fujitsu.com Tested-by: Lu Fengqi lufq.fnst@cn.fujitsu.com Signed-off-by: Anand Jain anand.jain@oracle.com Reviewed-by: David Sterba dsterba@suse.com [ update changelog ] 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/volumes.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
--- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -4517,7 +4517,12 @@ again:
/* Now btrfs_update_device() will change the on-disk size. */ ret = btrfs_update_device(trans, device); - btrfs_end_transaction(trans); + if (ret < 0) { + btrfs_abort_transaction(trans, ret); + btrfs_end_transaction(trans); + } else { + ret = btrfs_commit_transaction(trans); + } done: btrfs_free_path(path); if (ret) {