[syzbot] [fbdev?] general protection fault in bit_putcs

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2e530aeb342b Merge branch 'for-next/core', remote-tracking..
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=121c1fe6680000
kernel config: https://syzkaller.appspot.com/x/.config?x=5cc95add722fb0c1
dashboard link: https://syzkaller.appspot.com/bug?extid=524697c54d6e7ec67cf2
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10b93281680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1076e749680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2468ab4c933e/disk-2e530aeb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bd3708bf8a20/vmlinux-2e530aeb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/86bc7d3468f9/Image-2e530aeb.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+524697...@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address dfff800000000040
KASAN: null-ptr-deref in range [0x0000000000000200-0x0000000000000207]
Mem abort info:
ESR = 0x0000000096000005
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x05: level 1 translation fault
Data abort info:
ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000
CM = 0, WnR = 0, TnD = 0, TagAccess = 0
GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[dfff800000000040] address between user and kernel address ranges
Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 6015 Comm: syz-executor865 Not tainted 6.6.0-rc3-syzkaller-g2e530aeb342b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : __fb_pad_aligned_buffer include/linux/fb.h:629 [inline]
pc : bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
pc : bit_putcs+0x958/0xe30 drivers/video/fbdev/core/bitblit.c:185
lr : __fb_pad_aligned_buffer include/linux/fb.h:626 [inline]
lr : bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
lr : bit_putcs+0x93c/0xe30 drivers/video/fbdev/core/bitblit.c:185
sp : ffff800096a974a0
x29: ffff800096a976b0 x28: 0000000000000200 x27: ffff0000c8fb9010
x26: ffff0000c8fb9010 x25: 000000000000000f x24: dfff800000000000
x23: 0000000000000080 x22: 0000000000000000 x21: 0000000000000000
x20: ffff0000c0032440 x19: 0000000000000200 x18: ffff800096a96dc0
x17: ffff80008e19d000 x16: ffff80008a576f00 x15: 0000000000000009
x14: 1ffff00012d52ec1 x13: 0000000000000000 x12: 00000000ffffffff
x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
x8 : 0000000000000040 x7 : 0000000000000000 x6 : 0000000000000007
x5 : 0000000000000000 x4 : 0000000000000008 x3 : ffff8000831e57e8
x2 : 0000000000000800 x1 : 0000000000000010 x0 : 0000000000000000
Call trace:
__fb_pad_aligned_buffer include/linux/fb.h:629 [inline]
bit_putcs_aligned drivers/video/fbdev/core/bitblit.c:96 [inline]
bit_putcs+0x958/0xe30 drivers/video/fbdev/core/bitblit.c:185
fbcon_putcs+0x318/0x4e8 drivers/video/fbdev/core/fbcon.c:1282
do_update_region+0x42c/0x5f8 drivers/tty/vt/vt.c:623
redraw_screen+0x82c/0xd54 drivers/tty/vt/vt.c:983
fbcon_modechanged+0x9f4/0x1090 drivers/video/fbdev/core/fbcon.c:2703
fbcon_update_vcs+0x3c/0x4c drivers/video/fbdev/core/fbcon.c:2748
do_fb_ioctl+0xa68/0xd24 drivers/video/fbdev/core/fb_chrdev.c:92
fb_ioctl+0xec/0x134 drivers/video/fbdev/core/fb_chrdev.c:169
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl fs/ioctl.c:857 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:857
__invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:51
el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:136
do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:155
el0_svc+0x58/0x16c arch/arm64/kernel/entry-common.c:678
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:696
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:595
Code: 51000679 aa1c03f3 d343fe68 12000a69 (38f86908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 51000679 sub w25, w19, #0x1
4: aa1c03f3 mov x19, x28
8: d343fe68 lsr x8, x19, #3
c: 12000a69 and w9, w19, #0x7
* 10: 38f86908 ldrsb w8, [x8, x24] <-- trapping instruction


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