Commit 9845664b authored by David Sterba's avatar David Sterba
Browse files

btrfs: dev-replace: properly validate device names 

There's a syzbot report that device name buffers passed to device
replace are not properly checked for string termination which could lead
to a read out of bounds in getname_kernel().

Add a helper that validates both source and target device name buffers.
For devid as the source initialize the buffer to empty string in case
something tries to read it later.

This was originally analyzed and fixed in a different way by Edward Adam
Davis (see links).

Link: https://lore.kernel.org/linux-btrfs/000000000000d1a1d1060cc9c5e7@google.com/
Link: https://lore.kernel.org/linux-btrfs/tencent_44CA0665C9836EF9EEC80CB9E7E206DF5206@qq.com/


CC: stable@vger.kernel.org # 4.19+
CC: Edward Adam Davis <eadavis@qq.com>
Reported-and-tested-by: default avatar <syzbot+33f23b49ac24f986c9e8@syzkaller.appspotmail.com>
Reviewed-by: default avatarBoris Burkov <boris@bur.io>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 5906333c

fs/btrfs/dev-replace.c

+20 −4
Original line number Diff line number Diff line
@@ -725,6 +725,23 @@ static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info, 
	return ret;

}



static int btrfs_check_replace_dev_names(struct btrfs_ioctl_dev_replace_args *args)

{

	if (args->start.srcdevid == 0) {

		if (memchr(args->start.srcdev_name, 0,

			   sizeof(args->start.srcdev_name)) == NULL)

			return -ENAMETOOLONG;

	} else {

		args->start.srcdev_name[0] = 0;

	}



	if (memchr(args->start.tgtdev_name, 0,

		   sizeof(args->start.tgtdev_name)) == NULL)

	    return -ENAMETOOLONG;



	return 0;

}



int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,

			    struct btrfs_ioctl_dev_replace_args *args)

{
@@ -737,10 +754,9 @@ int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info, 
	default:

		return -EINVAL;

	}



	if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||

	    args->start.tgtdev_name[0] == '\0')

		return -EINVAL;

	ret = btrfs_check_replace_dev_names(args);

	if (ret < 0)

		return ret;



	ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,

					args->start.srcdevid,