linux-kernel - Re: [PATCH] block: fix memleak when __blk_rq_map_user

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Date:   Thu, 19 Dec 2019 16:27:37 +0800
From:   Bob Liu <bob.liu@...cle.com>
To:     Yang Yingliang <yangyingliang@...wei.com>, axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: fix memleak when __blk_rq_map_user_iov() is failed

On 12/18/19 4:44 PM, Yang Yingliang wrote:
> When I doing fuzzy test, get the memleak report:
> 
> BUG: memory leak
> unreferenced object 0xffff88837af80000 (size 4096):
>   comm "memleak", pid 3557, jiffies 4294817681 (age 112.499s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     20 00 00 00 10 01 00 00 00 00 00 00 01 00 00 00   ...............
>   backtrace:
>     [<000000001c894df8>] bio_alloc_bioset+0x393/0x590
>     [<000000008b139a3c>] bio_copy_user_iov+0x300/0xcd0
>     [<00000000a998bd8c>] blk_rq_map_user_iov+0x2f1/0x5f0
>     [<000000005ceb7f05>] blk_rq_map_user+0xf2/0x160
>     [<000000006454da92>] sg_common_write.isra.21+0x1094/0x1870
>     [<00000000064bb208>] sg_write.part.25+0x5d9/0x950
>     [<000000004fc670f6>] sg_write+0x5f/0x8c
>     [<00000000b0d05c7b>] __vfs_write+0x7c/0x100
>     [<000000008e177714>] vfs_write+0x1c3/0x500
>     [<0000000087d23f34>] ksys_write+0xf9/0x200
>     [<000000002c8dbc9d>] do_syscall_64+0x9f/0x4f0
>     [<00000000678d8e9a>] entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> If __blk_rq_map_user_iov() is failed in blk_rq_map_user_iov(),
> the bio(s) which is allocated before this failing will leak. The
> refcount of the bio(s) is init to 1 and increased to 2 by calling
> bio_get(), but __blk_rq_unmap_user() only decrease it to 1, so
> the bio cannot be freed. Fix it by calling blk_rq_unmap_user().
> 
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>

Good catch! Looks fine to me.
Reviewed-by: Bob Liu <bob.liu@...cle.com>

> ---
>  block/blk-map.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/block/blk-map.c b/block/blk-map.c
> index 3a62e471d81b..b0790268ed9d 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -151,7 +151,7 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
>  	return 0;
>  
>  unmap_rq:
> -	__blk_rq_unmap_user(bio);
> +	blk_rq_unmap_user(bio);
>  fail:
>  	rq->bio = NULL;
>  	return ret;
>