Re: [syzbot] [fbdev?] KASAN: vmalloc-out-of-bounds Write in imageblit (4)

[syzbot <syzbot+c4b7aa0513823e2ea880@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    c7fb1692dc01 Merge tag 'for-linus' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11742d63980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=660f6eb11f9c7dc5
dashboard link: https://syzkaller.appspot.com/bug?extid=c4b7aa0513823e2ea880
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11703653980000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=154565b7980000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-c7fb1692.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/246da487db6f/vmlinux-c7fb1692.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f0ea1e4dac0f/bzImage-c7fb1692.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c4b7aa0513823e2ea880@syzkaller.appspotmail.com

R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
 </TASK>
==================================================================
BUG: KASAN: vmalloc-out-of-bounds in fast_imageblit drivers/video/fbdev/core/sysimgblt.c:257 [inline]
BUG: KASAN: vmalloc-out-of-bounds in sys_imageblit+0x1ec6/0x2b00 drivers/video/fbdev/core/sysimgblt.c:326
Write of size 4 at addr ffffc90001c41000 by task syz-executor161/5103

CPU: 0 UID: 0 PID: 5103 Comm: syz-executor161 Not tainted 6.11.0-rc6-syzkaller-00048-gc7fb1692dc01 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 fast_imageblit drivers/video/fbdev/core/sysimgblt.c:257 [inline]
 sys_imageblit+0x1ec6/0x2b00 drivers/video/fbdev/core/sysimgblt.c:326
 drm_fbdev_shmem_defio_imageblit+0x2e/0x100 drivers/gpu/drm/drm_fbdev_shmem.c:39
 bit_putcs+0x18ba/0x1db0
 fbcon_putcs+0x255/0x390 drivers/video/fbdev/core/fbcon.c:1288
 do_update_region+0x396/0x450 drivers/tty/vt/vt.c:619
 redraw_screen+0x902/0xe90 drivers/tty/vt/vt.c:971
 con2fb_init_display drivers/video/fbdev/core/fbcon.c:794 [inline]
 set_con2fb_map+0xa6c/0x10a0 drivers/video/fbdev/core/fbcon.c:865
 fbcon_set_con2fb_map_ioctl+0x207/0x320 drivers/video/fbdev/core/fbcon.c:3092
 do_fb_ioctl+0x38f/0x7b0 drivers/video/fbdev/core/fb_chrdev.c:138
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7feb9b353729
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 1a 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffde9b9f968 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffde9b9f980 RCX: 00007feb9b353729
RDX: 00000000200000c0 RSI: 0000000000004610 RDI: 0000000000000003
RBP: 0000000000000001 R08: 00007ffde9b9f707 R09: 00000000000000a0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
 </TASK>

The buggy address belongs to the virtual mapping at
 [ffffc90001941000, ffffc90001c42000) created by:
 drm_gem_shmem_vmap+0x3ac/0x630 drivers/gpu/drm/drm_gem_shmem_helper.c:343

Memory state around the buggy address:
 ffffc90001c40f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90001c40f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90001c41000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffffc90001c41080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90001c41100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================


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