Mysterious operations in sysimgblt.c and sysimgblt.c
From: Igor Torrente <hidden>
Date: 2021-05-14 14:12:11
Also in:
dri-devel, lkml
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