| Summary: | xorg crashes when v4l module is loaded on AMD64 | ||||||||
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| Product: | xorg | Reporter: | Frédéric Giquel <fgiquel> | ||||||
| Component: | Driver/other | Assignee: | Xorg Project Team <xorg-team> | ||||||
| Status: | RESOLVED FIXED | QA Contact: | Xorg Project Team <xorg-team> | ||||||
| Severity: | critical | ||||||||
| Priority: | medium | CC: | ppaalanen, spam | ||||||
| Version: | 7.1 (2006.05) | ||||||||
| Hardware: | x86-64 (AMD64) | ||||||||
| OS: | Linux (All) | ||||||||
| Whiteboard: | |||||||||
| i915 platform: | i915 features: | ||||||||
| Attachments: |
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We just got another report about this bug in the Debian BTS (http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=422008). Same problem, xvinfo crashes the server when the v4l module is loaded. It was with the ATI driver instead of NV this time, still on AMD64. Since the submitter of this bug already posted an explanation of the bug and a possible fix, it'd be nice if somebody could look at it. Thanks, Brice the problem is also present in xorg 7.2 :-/ This bug is the closest match to what I experienced right now on Gentoo, using xorg-server 1.4.0.90 from Gentoo official packages. I have a tv-card which works with the bttv driver. If bttv is loaded when X starts, running xvinfo makes X segfault somewhere in dispatch(), the backtrace seems quite useless. If bttv is not loaded during X startup, xvinfo works fine. I can load bttv and xvinfo continues to work fine in the current X session. And I can watch tv with tvtime. And yes, this is amd64 architecture. Created attachment 15371 [details]
Xorg log with my crash
Created attachment 15372 [details]
Gdb session
Here's the gdb session I did today, with x11-base/xorg-server-1.4.0.90-r3 in Gentoo. It shows a NULL pointer dereference in Dispatch(), dispatch.c:459.
The crash goes away if I remove Load "v4l" from config, or unload bttv driver.
This code was completely changed in February. I suggest you try current git, and if that doesn't work, contact Mauro Carvalho Chehab <mchehab@redhat.com> |
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Using xvinfo makes xorg crashes when v4l module is loaded. It's reproducible. I've found the reason of the crash. It's related to the 64 bits architecture. The explanation : - line 648 of v4l.c : ioctl(V4L_FD,VIDIOCGFREQ,value); - line 612 of v4l.c : we know that value is INT32 * - in videodev.h : #define VIDIOCGFREQ _IOR('v',14, unsigned long) With 32 bits architecture, long is 32 bits and there's no problem. With 64 bits architecture like AMD64, long is 64 bits and ioctl try to write to the double-word *value and an unauthorized double-word near *value. So xorg crashes. To temporally fix the bug, I replace the line 648 of v4l.c with the next 3 lines : unsigned long freq; ioctl(V4L_FD,VIDIOCGFREQ,&freq); *value = (INT32) freq; There is no crash anymore with xvinfo. We lose some information (64 bits -> 32 bits) but it seems unimportant (the frequency value is between 0 and 16000 according to line 190 of v4l.c). Perhaps, a better solution can be found... We certainly have the same problem with VIDIOCSFREQ to set the frequency (line 597 of v4l.c) but I didn't try anything. If other information is needed, the debian bug report : http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=413640