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From: Igor Torrente <igormtorrente@gmail.com>
To: adaplas@hotpop.com, akpm@osdl.org, jsimmons@infradead.org
Cc: linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org,
	dri-devel@lists.freedesktop.org
Subject: Mysterious operations in sysimgblt.c and sysimgblt.c
Date: Fri, 14 May 2021 11:11:57 -0300	[thread overview]
Message-ID: <027b5b6a-54ea-37e6-7b9f-26f4bad29514@gmail.com> (raw)

Hello everybody,

I'm Igor, I'm participating in the Linux kernel mentorship program and 
working to fix some bugs found by the syzbot. I'm currently working on 
this bug below:

https://syzkaller.appspot.com/bug?id=071122e4f772c1ec834c7a6facc0b5058d215481

The bug consists of an out-of-bound access of an vmalloc vector at the 
imageblit function.

At this moment, I'm trying to understand what is happening between the 
IOCTL and the imageblit function. I tried to follow the commit history, 
but even with the entire history, and after reading the code several 
times, I have no clue why some operations are being done. Operations like:

Lines 148 and 177-180: 
https://elixir.bootlin.com/linux/v5.13-rc1/source/drivers/video/fbdev/core/bitblit.c#L148
Lines 251-256: 
https://elixir.bootlin.com/linux/v5.13-rc1/source/drivers/video/fbdev/core/sysimgblt.c#L251
Line 190: 
https://elixir.bootlin.com/linux/v5.13-rc1/source/drivers/video/fbdev/core/sysimgblt.c#L190

Anyone know/remember what these operations are doing?

Thanks for your attention,
---
Igor M. A. Torrente

                 reply	other threads:[~2021-05-14 14:12 UTC|newest]

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