On Fri, Jul 27, 2018 at 1:04 AM, Naohiro Aota <naota@xxxxxxxxx> wrote:
> When btrfs hits error after modifying fs_devices in
> btrfs_init_new_device() (such as btrfs_add_dev_item() returns error), it
> leaves everything as is, but frees allocated btrfs_device. As a result,
> fs_devices->devices and fs_devices->alloc_list contain already freed
> btrfs_device, leading to later use-after-free bug.
>
> Error path also messes the things like ->num_devices. While they go backs
> to the original value by unscanning btrfs devices, it is safe to revert
> them here.
>
> Fixes: 79787eaab461 ("btrfs: replace many BUG_ONs with proper error handling")
> Signed-off-by: Naohiro Aota <naota@xxxxxxxxx>
Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx>
Looks good, only fs_info->fs_devices->rotating isn't restored but
currently that causes no problems.
> ---
> fs/btrfs/volumes.c | 28 +++++++++++++++++++++++-----
> 1 file changed, 23 insertions(+), 5 deletions(-)
>
> This patch applies on master, but not on kdave/for-next because of
> 74b9f4e186eb ("btrfs: declare fs_devices in btrfs_init_new_device()")
>
> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
> index 1da162928d1a..5f0512fffa52 100644
> --- a/fs/btrfs/volumes.c
> +++ b/fs/btrfs/volumes.c
> @@ -2410,7 +2410,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
> struct list_head *devices;
> struct super_block *sb = fs_info->sb;
> struct rcu_string *name;
> - u64 tmp;
> + u64 orig_super_total_bytes, orig_super_num_devices;
> int seeding_dev = 0;
> int ret = 0;
> bool unlocked = false;
> @@ -2509,12 +2509,14 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
> if (!blk_queue_nonrot(q))
> fs_info->fs_devices->rotating = 1;
>
> - tmp = btrfs_super_total_bytes(fs_info->super_copy);
> + orig_super_total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
> btrfs_set_super_total_bytes(fs_info->super_copy,
> - round_down(tmp + device->total_bytes, fs_info->sectorsize));
> + round_down(orig_super_total_bytes + device->total_bytes,
> + fs_info->sectorsize));
>
> - tmp = btrfs_super_num_devices(fs_info->super_copy);
> - btrfs_set_super_num_devices(fs_info->super_copy, tmp + 1);
> + orig_super_num_devices = btrfs_super_num_devices(fs_info->super_copy);
> + btrfs_set_super_num_devices(fs_info->super_copy,
> + orig_super_num_devices + 1);
>
> /* add sysfs device entry */
> btrfs_sysfs_add_device_link(fs_info->fs_devices, device);
> @@ -2594,6 +2596,22 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
>
> error_sysfs:
> btrfs_sysfs_rm_device_link(fs_info->fs_devices, device);
> + mutex_lock(&fs_info->fs_devices->device_list_mutex);
> + mutex_lock(&fs_info->chunk_mutex);
> + list_del_rcu(&device->dev_list);
> + list_del(&device->dev_alloc_list);
> + fs_info->fs_devices->num_devices--;
> + fs_info->fs_devices->open_devices--;
> + fs_info->fs_devices->rw_devices--;
> + fs_info->fs_devices->total_devices--;
> + fs_info->fs_devices->total_rw_bytes -= device->total_bytes;
> + atomic64_sub(device->total_bytes, &fs_info->free_chunk_space);
> + btrfs_set_super_total_bytes(fs_info->super_copy,
> + orig_super_total_bytes);
> + btrfs_set_super_num_devices(fs_info->super_copy,
> + orig_super_num_devices);
> + mutex_unlock(&fs_info->chunk_mutex);
> + mutex_unlock(&fs_info->fs_devices->device_list_mutex);
> error_trans:
> if (seeding_dev)
> sb->s_flags |= SB_RDONLY;
> --
> 2.18.0
>
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--
Filipe David Manana,
“Whether you think you can, or you think you can't — you're right.”
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