On 4/10/22 11:02, Ondrej Zary wrote: > On Friday 08 April 2022 03:58:10 Zheyu Ma wrote: >> On Fri, Apr 8, 2022 at 3:50 AM Helge Deller <deller@xxxxxx> wrote: >>> >>> On 4/4/22 10:47, Zheyu Ma wrote: >>>> The userspace program could pass any values to the driver through >>>> ioctl() interface. If the driver doesn't check the value of 'pixclock', >>>> it may cause divide error. >>>> >>>> Fix this by checking whether 'pixclock' is zero in the function >>>> i740fb_check_var(). >>>> >>>> The following log reveals it: >>>> >>>> divide error: 0000 [#1] PREEMPT SMP KASAN PTI >>>> RIP: 0010:i740fb_decode_var drivers/video/fbdev/i740fb.c:444 [inline] >>>> RIP: 0010:i740fb_set_par+0x272f/0x3bb0 drivers/video/fbdev/i740fb.c:739 >>>> Call Trace: >>>> fb_set_var+0x604/0xeb0 drivers/video/fbdev/core/fbmem.c:1036 >>>> do_fb_ioctl+0x234/0x670 drivers/video/fbdev/core/fbmem.c:1112 >>>> fb_ioctl+0xdd/0x130 drivers/video/fbdev/core/fbmem.c:1191 >>>> vfs_ioctl fs/ioctl.c:51 [inline] >>>> __do_sys_ioctl fs/ioctl.c:874 [inline] >>>> >>>> Signed-off-by: Zheyu Ma <zheyuma97@xxxxxxxxx> >>> >>> Hello Zheyu, >>> >>> I've applied the patches #2-#7 of this series, but left >>> out this specific patch (for now). >>> As discussed on the mailing list we can try to come up with a >>> better fix (to round up the pixclock when it's invalid). >>> If not, I will apply this one later. >> >> I'm also looking forward to a more appropriate patch for this driver! > > I was not able to reproduce it at first but finally found it: the > monitor must be unplugged. If a valid EDID is present, > fb_validate_mode() call in i740fb_check_var() will refuse zero > pixclock. > > Haven't found any obvious way to correct zero pixclock value. Most other drivers simply return -EINVAL. Thanks for checking, Ondrej! So, I'll apply the EINVAL-patch from Zheyu for now. Helge
