On 2018/11/23 下午6:10, Pan Bian wrote:
> The function relocate_block_group calls btrfs_end_transaction to release
> trans when update_backref_cache returns 1, and then continues the loop
> body. If btrfs_block_rsv_refill fails this time, it will jump out the
> loop and the freed trans will be accessed. This may result in a
> use-after-free bug. The patch assigns NULL to trans after trans is
> released so that it will not be accessed.
>
> Fixes: 0647bf564f1("Btrfs: improve forever loop when doing balance
> relocation")
>
> Signed-off-by: Pan Bian <bianpan2016@xxxxxxx>
Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>
Thanks,
Qu
> ---
> fs/btrfs/relocation.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
> index 924116f..a3f75b8 100644
> --- a/fs/btrfs/relocation.c
> +++ b/fs/btrfs/relocation.c
> @@ -3959,6 +3959,7 @@ static noinline_for_stack int relocate_block_group(struct reloc_control *rc)
> restart:
> if (update_backref_cache(trans, &rc->backref_cache)) {
> btrfs_end_transaction(trans);
> + trans = NULL;
> continue;
> }
>
>
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