kernel panic: stack is corrupted in get_kernel_gp_address

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f4d51dff Linux 5.9-rc4
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14aa2d3e900000
kernel config: https://syzkaller.appspot.com/x/.config?x=a9075b36a6ae26c9
dashboard link: https://syzkaller.appspot.com/bug?extid=d6459d8f8984c0929e54
compiler: gcc (GCC) 10.1.0-syz 20200507
userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=164270dd900000

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

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13c7d9f9900000
final oops: https://syzkaller.appspot.com/x/report.txt?x=1027d9f9900000
console output: https://syzkaller.appspot.com/x/log.txt?x=17c7d9f9900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d6459d...@syzkaller.appspotmail.com

���ACode: Bad RIP value.
Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: get_kernel_gp_address+0x1a0/0x1c0 arch/x86/kernel/traps.c:520
Kernel Offset: disabled


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
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[syzbot]

syzbot suspects this issue was fixed by commit:

commit a49145acfb975d921464b84fe00279f99827d816
Author: George Kennedy <george....@oracle.com>
Date: Tue Jul 7 19:26:03 2020 +0000

fbmem: add margin check to fb_check_caps()

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10ff7572500000
start commit: f4d51dff Linux 5.9-rc4
git tree: upstream

kernel config: https://syzkaller.appspot.com/x/.config?x=a9075b36a6ae26c9
dashboard link: https://syzkaller.appspot.com/bug?extid=d6459d8f8984c0929e54

userspace arch: i386
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=164270dd900000

If the result looks correct, please mark the issue as fixed by replying with:

#syz fix: fbmem: add margin check to fb_check_caps()

[Dmitry Vyukov]

[syzbot]

> #syz fix: fbmem: add margin check to fb_check_caps()

Your 'fix:' command is accepted, but please keep syzkall...@googlegroups.com mailing list in CC next time. It serves as a history of what happened with each bug report. Thank you.