BUG: unable to handle kernel paging request in cfb_imageblit

Tue Oct 6 08:18:16 UTC 2020

Hello,

syzbot found the following issue on:

HEAD commit:    22fbc037 Merge tag 'for-linus' of git://git.kernel.org/pub..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=133731eb900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4e672827d2ffab1f
dashboard link: https://syzkaller.appspot.com/bug?extid=dfd0b1c6705301cc4847
compiler:       clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11ba9a5d900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17cfd4af900000

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

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1536a750500000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=1736a750500000
console output: https://syzkaller.appspot.com/x/log.txt?x=1336a750500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dfd0b1c6705301cc4847 at syzkaller.appspotmail.com

BUG: unable to handle page fault for address: ffff888001000018
#PF: supervisor write access in kernel mode
#PF: error_code(0x0003) - permissions violation
PGD c801067 P4D c801067 PUD c802067 PMD 80000000010001e1 
Oops: 0003 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 8241 Comm: syz-executor265 Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__writel arch/x86/include/asm/io.h:71 [inline]
RIP: 0010:slow_imageblit drivers/video/fbdev/core/cfbimgblt.c:178 [inline]
RIP: 0010:cfb_imageblit+0xb15/0x11e0 drivers/video/fbdev/core/cfbimgblt.c:302
Code: 89 e6 89 e9 41 d3 e6 41 09 de 89 ef 8b 5c 24 28 89 de e8 0e db 81 fd 39 dd 73 0a e8 65 d9 81 fd eb 42 0f 1f 00 48 8b 44 24 30 <44> 89 30 48 83 c0 04 48 89 44 24 30 89 ef 89 de e8 e6 da 81 fd 39
RSP: 0018:ffffc9000a037558 EFLAGS: 00010246
RAX: ffff888001000018 RBX: 000000000000001c RCX: 000000000000001c
RDX: ffff8880a79880c0 RSI: 000000000000001c RDI: 000000000000001c
RBP: 000000000000001c R08: ffffffff83f32412 R09: ffffffff83f31b7c
R10: 0000000000000002 R11: ffff8880a79880c0 R12: 0000000000000000
R13: ffff888218a81f72 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f8534532700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff888001000018 CR3: 00000000a80b4000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 soft_cursor+0xb44/0xdb0 drivers/video/fbdev/core/softcursor.c:74
 bit_cursor+0x1753/0x2110 drivers/video/fbdev/core/bitblit.c:377
 set_cursor drivers/tty/vt/vt.c:919 [inline]
 con_flush_chars+0x4e1/0x640 drivers/tty/vt/vt.c:3330
 con_write+0x2a/0x40 drivers/tty/vt/vt.c:3251
 do_output_char+0x63b/0x940 drivers/tty/n_tty.c:447
 __process_echoes+0x2a3/0x930 drivers/tty/n_tty.c:739
 flush_echoes drivers/tty/n_tty.c:829 [inline]
 __receive_buf drivers/tty/n_tty.c:1648 [inline]
 n_tty_receive_buf_common+0x29fa/0x3100 drivers/tty/n_tty.c:1742
 paste_selection+0x32c/0x450 drivers/tty/vt/selection.c:408
 vt_ioctl+0x105a/0x3d70 drivers/tty/vt/vt_ioctl.c:862
 tty_ioctl+0xee4/0x15c0 drivers/tty/tty_io.c:2656
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x449809
Code: e8 8c e7 ff ff 48 83 c4 18 c3 0f 1f 80 00 00 00 00 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 0f 83 5b 05 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f8534531db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000006dec68 RCX: 0000000000449809
RDX: 0000000020000080 RSI: 000000000000541c RDI: 0000000000000007
RBP: 00000000006dec60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dec6c
R13: 00007ffe8074321f R14: 00007f85345329c0 R15: 0000000000000064
Modules linked in:
CR2: ffff888001000018
---[ end trace 4ec628432d38a26a ]---
RIP: 0010:__writel arch/x86/include/asm/io.h:71 [inline]
RIP: 0010:slow_imageblit drivers/video/fbdev/core/cfbimgblt.c:178 [inline]
RIP: 0010:cfb_imageblit+0xb15/0x11e0 drivers/video/fbdev/core/cfbimgblt.c:302
Code: 89 e6 89 e9 41 d3 e6 41 09 de 89 ef 8b 5c 24 28 89 de e8 0e db 81 fd 39 dd 73 0a e8 65 d9 81 fd eb 42 0f 1f 00 48 8b 44 24 30 <44> 89 30 48 83 c0 04 48 89 44 24 30 89 ef 89 de e8 e6 da 81 fd 39
RSP: 0018:ffffc9000a037558 EFLAGS: 00010246
RAX: ffff888001000018 RBX: 000000000000001c RCX: 000000000000001c
RDX: ffff8880a79880c0 RSI: 000000000000001c RDI: 000000000000001c
RBP: 000000000000001c R08: ffffffff83f32412 R09: ffffffff83f31b7c
R10: 0000000000000002 R11: ffff8880a79880c0 R12: 0000000000000000
R13: ffff888218a81f72 R14: 0000000000000000 R15: 0000000000000000
FS:  00007f8534532700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff888001000018 CR3: 00000000a80b4000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

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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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