linux-kernel - Re: [PATCH 2/2] ubi: Fix unreferenced object reported by kmemleak in ubi_resize

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Date:   Fri, 21 Oct 2022 21:24:48 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     Li Zetao <lizetao1@...wei.com>, <richard@....at>,
        <miquel.raynal@...tlin.com>, <vigneshr@...com>,
        <dedekind@...utronix.de>, <haver@...t.ibm.com>,
        <bbrezillon@...nel.org>
CC:     <boris.brezillon@...e-electrons.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] ubi: Fix unreferenced object reported by kmemleak in
 ubi_resize_volume()

在 2022/10/21 18:21, Li Zetao 写道:
> There is a memory leaks problem reported by kmemleak:
>
> unreferenced object 0xffff888102007a00 (size 128):
>    comm "ubirsvol", pid 32090, jiffies 4298464136 (age 2361.231s)
>    hex dump (first 32 bytes):
> ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff  ................
> ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff  ................
>    backtrace:
> [<ffffffff8176cecd>] __kmalloc+0x4d/0x150
> [<ffffffffa02a9a36>] ubi_eba_create_table+0x76/0x170 [ubi]
> [<ffffffffa029764e>] ubi_resize_volume+0x1be/0xbc0 [ubi]
> [<ffffffffa02a3321>] ubi_cdev_ioctl+0x701/0x1850 [ubi]
> [<ffffffff81975d2d>] __x64_sys_ioctl+0x11d/0x170
> [<ffffffff83c142a5>] do_syscall_64+0x35/0x80
> [<ffffffff83e0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
> This is due to a mismatch between create and destroy interfaces, and
> in detail that "new_eba_tbl" created by ubi_eba_create_table() but
> destroyed by kfree(), while will causing "new_eba_tbl->entries" not
> freed.
>
> Fix it by replacing kfree(new_eba_tbl) with
> ubi_eba_destroy_table(new_eba_tbl)
>
> Fixes: 799dca34ac54 ("UBI: hide EBA internals")
> Signed-off-by: Li Zetao <lizetao1@...wei.com>
> ---
>   drivers/mtd/ubi/vmt.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
> index 74637575346e..9fbc64b997ce 100644
> --- a/drivers/mtd/ubi/vmt.c
> +++ b/drivers/mtd/ubi/vmt.c
> @@ -515,7 +515,7 @@ int ubi_resize_volume(struct ubi_volume_desc *desc, int reserved_pebs)
>   	return err;
>   
>   out_free:
> -	kfree(new_eba_tbl);
> +	ubi_eba_destroy_table(new_eba_tbl);
>   	return err;
>   }
>   

Reviewed-by: Zhihao Cheng <chengzhihao1@...wei.com>