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Date:   Thu, 6 May 2021 17:57:22 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     Uladzislau Rezki <urezki@gmail.com>
Cc:     linux-usb@vger.kernel.org, linux-media@vger.kernel.org,
        linux-kernel@vger.kernel.org, mchehab@kernel.org,
        syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] WARNING in __vmalloc_node_range
Message-ID: <20210506145722.GC1955@kadam>
References: <000000000000fdc0be05c1a6d68f@google.com>
 <20210506142210.GA37570@pc638.lan>
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On Thu, May 06, 2021 at 04:22:10PM +0200, Uladzislau Rezki wrote:
> Seems like vmalloc() is called with zero size passed:
> 
> <snip>
> void *__vmalloc_node_range(unsigned long size, unsigned long align,
> 			unsigned long start, unsigned long end, gfp_t gfp_mask,
> 			pgprot_t prot, unsigned long vm_flags, int node,
> 			const void *caller)
> {
> 	struct vm_struct *area;
> 	void *addr;
> 	unsigned long real_size = size;
> 	unsigned long real_align = align;
> 	unsigned int shift = PAGE_SHIFT;
> 
> 2873	if (WARN_ON_ONCE(!size))
> 		return NULL;
> <snip>
> 
> from the dvb_dmx_init() driver:
> 
> <snip>
> int dvb_dmx_init(struct dvb_demux *dvbdemux)
> {
> 	int i;
> 	struct dmx_demux *dmx = &dvbdemux->dmx;
> 
> 	dvbdemux->cnt_storage = NULL;
> 	dvbdemux->users = 0;
> 1251	dvbdemux->filter = vmalloc(array_size(sizeof(struct dvb_demux_filter),
> <snip>					      dvbdemux->filternum));

Indeed.

It is a mystery because array_size() should never return less than
sizeof(struct dvb_demux_filter).  That's the whole point of the
array_size() function is that it returns ULONG_MAX if there is an
integer overflow.

regards,
dan carpenter