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From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Chen Huang <chenhuang5@huawei.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Randy Dunlap <rdunlap@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-mm <linux-mm@kvack.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [BUG] arm64: an infinite loop in generic_perform_write()
Date: Thu, 24 Jun 2021 12:15:46 +0100	[thread overview]
Message-ID: <YNRpYli/5/GWvaTT@casper.infradead.org> (raw)
In-Reply-To: <YNQuZ8ykN7aR+1MP@infradead.org>

On Thu, Jun 24, 2021 at 08:04:07AM +0100, Christoph Hellwig wrote:
> On Thu, Jun 24, 2021 at 04:24:46AM +0100, Matthew Wilcox wrote:
> > On Thu, Jun 24, 2021 at 11:10:41AM +0800, Chen Huang wrote:
> > > In userspace, I perform such operation:
> > > 
> > >  	fd = open("/tmp/test", O_RDWR | O_SYNC);
> > >         access_address = (char *)mmap(NULL, uio_size, PROT_READ, MAP_SHARED, uio_fd, 0);
> > >         ret = write(fd, access_address + 2, sizeof(long));
> > 
> > ... you know that accessing this at unaligned offsets isn't going to
> > work.  It's completely meaningless.  Why are you trying to do it?
> 
> We still should not cause an infinite loop in kernel space due to a
> a userspace programmer error.

They're running as root and they've mapped some device memory.  We can't
save them from themself.  Imagine if they'd done this to the NVMe BAR.

WARNING: multiple messages have this Message-ID (diff)
From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: Chen Huang <chenhuang5@huawei.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Randy Dunlap <rdunlap@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	linux-mm <linux-mm@kvack.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [BUG] arm64: an infinite loop in generic_perform_write()
Date: Thu, 24 Jun 2021 12:15:46 +0100	[thread overview]
Message-ID: <YNRpYli/5/GWvaTT@casper.infradead.org> (raw)
In-Reply-To: <YNQuZ8ykN7aR+1MP@infradead.org>

On Thu, Jun 24, 2021 at 08:04:07AM +0100, Christoph Hellwig wrote:
> On Thu, Jun 24, 2021 at 04:24:46AM +0100, Matthew Wilcox wrote:
> > On Thu, Jun 24, 2021 at 11:10:41AM +0800, Chen Huang wrote:
> > > In userspace, I perform such operation:
> > > 
> > >  	fd = open("/tmp/test", O_RDWR | O_SYNC);
> > >         access_address = (char *)mmap(NULL, uio_size, PROT_READ, MAP_SHARED, uio_fd, 0);
> > >         ret = write(fd, access_address + 2, sizeof(long));
> > 
> > ... you know that accessing this at unaligned offsets isn't going to
> > work.  It's completely meaningless.  Why are you trying to do it?
> 
> We still should not cause an infinite loop in kernel space due to a
> a userspace programmer error.

They're running as root and they've mapped some device memory.  We can't
save them from themself.  Imagine if they'd done this to the NVMe BAR.

_______________________________________________
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-06-24 11:17 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-23  2:39 [BUG] arm64: an infinite loop in generic_perform_write() Chen Huang
2021-06-23  2:39 ` Chen Huang
2021-06-23  2:50 ` Al Viro
2021-06-23  2:50   ` Al Viro
2021-06-23  3:24   ` Xiaoming Ni
2021-06-23  3:24     ` Xiaoming Ni
2021-06-23  4:27     ` Al Viro
2021-06-23  4:27       ` Al Viro
2021-06-23  9:32       ` Catalin Marinas
2021-06-23  9:32         ` Catalin Marinas
2021-06-23 11:51         ` Matthew Wilcox
2021-06-23 11:51           ` Matthew Wilcox
2021-06-23 13:04         ` Al Viro
2021-06-23 13:04           ` Al Viro
2021-06-23 13:22 ` Mark Rutland
2021-06-23 13:22   ` Mark Rutland
2021-06-24  3:10   ` Chen Huang
2021-06-24  3:10     ` Chen Huang
2021-06-24  3:24     ` Matthew Wilcox
2021-06-24  3:24       ` Matthew Wilcox
2021-06-24  3:52       ` Chen Huang
2021-06-24  3:52         ` Chen Huang
2021-06-24  7:04       ` Christoph Hellwig
2021-06-24  7:04         ` Christoph Hellwig
2021-06-24 11:15         ` Matthew Wilcox [this message]
2021-06-24 11:15           ` Matthew Wilcox
2021-06-24 13:22           ` Robin Murphy
2021-06-24 13:22             ` Robin Murphy
2021-06-24 16:27             ` Al Viro
2021-06-24 16:27               ` Al Viro
2021-06-24 16:38               ` Robin Murphy
2021-06-24 16:38                 ` Robin Murphy
2021-06-24 16:39                 ` Al Viro
2021-06-24 16:39                   ` Al Viro
2021-06-24 17:24                   ` Robin Murphy
2021-06-24 17:24                     ` Robin Murphy
2021-06-24 18:55               ` Catalin Marinas
2021-06-24 18:55                 ` Catalin Marinas
2021-06-24 20:36                 ` Robin Murphy
2021-06-24 20:36                   ` Robin Murphy
2021-06-25 10:39                   ` Catalin Marinas
2021-06-25 10:39                     ` Catalin Marinas
2021-06-28 16:22                     ` Robin Murphy
2021-06-28 16:22                       ` Robin Murphy
2021-06-29  8:30                       ` Catalin Marinas
2021-06-29  8:30                         ` Catalin Marinas
2021-06-29 10:01                         ` Robin Murphy
2021-06-29 10:01                           ` Robin Murphy
2021-07-06 17:50                       ` Catalin Marinas
2021-07-06 17:50                         ` Catalin Marinas
2021-07-06 19:15                         ` Robin Murphy
2021-07-06 19:15                           ` Robin Murphy
2021-07-07  9:55                           ` David Laight
2021-07-07  9:55                             ` David Laight
2021-07-07 11:04                             ` Robin Murphy
2021-07-07 11:04                               ` Robin Murphy
2021-07-07 12:50                           ` Catalin Marinas
2021-07-07 12:50                             ` Catalin Marinas
2021-06-24 15:09           ` Catalin Marinas
2021-06-24 15:09             ` Catalin Marinas
2021-06-24 16:17             ` Al Viro
2021-06-24 16:17               ` Al Viro

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