kernel panic: Fatal exception (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: de2e69cf Add linux-next specific files for 20200721
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10e0f437100000
kernel config: https://syzkaller.appspot.com/x/.config?x=a18f913b3827a63a
dashboard link: https://syzkaller.appspot.com/bug?extid=c05fb1e489a39618f063
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16aaaa44900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16eee678900000

Bisection is inconclusive: the issue happens on the oldest tested release.

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=110e6b7f100000
final oops: https://syzkaller.appspot.com/x/report.txt?x=130e6b7f100000
console output: https://syzkaller.appspot.com/x/log.txt?x=150e6b7f100000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c05fb1...@syzkaller.appspotmail.com

R10: 0000000000000000 R11: 0000000000063688 R12: ffff88809f129000
R13: ffff8880a47e5000 R14: 0000000000008000 R15: ffffffff889943e0
FS: 0000000000000000(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004553d0 CR3: 000000009cd20000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Kernel panic - not syncing: Fatal exception
Kernel Offset: disabled
Rebooting in 86400 seconds..


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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
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[Tetsuo Handa]

#syz dup: general protection fault in do_con_write

Source code location of RIP: line in the report is not available, but similar
reproducer in my environment says vc->vc_size_row == 0 in fbcon_update_softback().

Then, this case should be avoided by "vt: Reject zero-sized screen buffer size."
which refuses screen with 0 row or 0 column.