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Message-ID: <1564398922.25582.6.camel@suse.com>
Date: Mon, 29 Jul 2019 13:15:22 +0200
From: Oliver Neukum <oneukum@...e.com>
To: Jia-Ju Bai <baijiaju1990@...il.com>, gregkh@...uxfoundation.org,
stern@...land.harvard.edu
Cc: usb-storage@...ts.one-eyed-alien.net, linux-kernel@...r.kernel.org,
linux-usb@...r.kernel.org
Subject: Re: [PATCH] usb: storage: sddr55: Fix a possible null-pointer
dereference in sddr55_transport()
Am Montag, den 29.07.2019, 18:05 +0800 schrieb Jia-Ju Bai:
Hi,
> In sddr55_transport(), there is an if statement on line 836 to check
> whether info->lba_to_pba is NULL:
> if (info->lba_to_pba == NULL || ...)
>
> When info->lba_to_pba is NULL, it is used on line 948:
> pba = info->lba_to_pba[lba];
>
> Thus, a possible null-pointer dereference may occur.
Yes, in practice READ_CAPACITY will always be called and set
up the correct translation table, but you can probably exploit
this.
> To fix this bug, info->lba_to_pba is checked before being used.
>
> This bug is found by a static analysis tool STCheck written by us.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
> ---
> drivers/usb/storage/sddr55.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/storage/sddr55.c b/drivers/usb/storage/sddr55.c
> index b8527c55335b..50afc39aa21d 100644
> --- a/drivers/usb/storage/sddr55.c
> +++ b/drivers/usb/storage/sddr55.c
> @@ -945,7 +945,8 @@ static int sddr55_transport(struct scsi_cmnd *srb, struct us_data *us)
> return USB_STOR_TRANSPORT_FAILED;
> }
>
> - pba = info->lba_to_pba[lba];
> + if (info->lba_to_pba)
> + pba = info->lba_to_pba[lba];
If you use that fix, pba will be uninitialized when used. It should be
something like:
pba = info->lba_to_pba ? info->lba_to_pba[lba] : 0;
Regards
Oliver
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