(We analyzed the crash and added the result below.) We report the crash: "KASAN: use-after-free Read in vgacon_invert_region" This crash was found in v4.17-rc3. Specifically, memory access (read operation) is invalid and which is detected by KASAN. Analysis: The function "vt_do_resize" basically allows for resizing the screen buffer (i.e., vc_data) beyond memory address 0x100000 (i.e., 0xffff880000100000 in this case). We think, however, a certain memory area starting from 0x100000 is protected. So subsequent memory access beyond this address (by "vgacon_invert_region") causes memory access violation. C repro code: https://kiwi.cs.purdue.edu/static/alexkkid-fuzzer/repro-ba6c1.c kernel config: https://kiwi.cs.purdue.edu/static/alexkkid-fuzzer/kernel-config-v4.17-rc3 Crash log: ============================================================== BUG: KASAN: use-after-free in vgacon_invert_region+0xf9/0x100 drivers/video/console/vgacon.c:663 Read of size 2 at addr ffff880000100000 by task syz-executor3/525 CPU: 0 PID: 525 Comm: syz-executor3 Not tainted 4.17.0-rc3 #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xc7/0x138 lib/dump_stack.c:113 print_address_description+0x78/0x290 mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report+0x234/0x350 mm/kasan/report.c:412 __asan_report_load2_noabort+0x19/0x20 mm/kasan/report.c:431 vgacon_invert_region+0xf9/0x100 drivers/video/console/vgacon.c:663 invert_screen+0x197/0x630 drivers/tty/vt/vt.c:461 highlight drivers/tty/vt/selection.c:51 [inline] set_selection+0x6b7/0xf60 drivers/tty/vt/selection.c:276 tioclinux+0x126/0x410 drivers/tty/vt/vt.c:2691 vt_ioctl+0x1036/0x2580 drivers/tty/vt/vt_ioctl.c:362 tty_ioctl+0x288/0x14c0 drivers/tty/tty_io.c:2646 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x191/0xfe0 fs/ioctl.c:686 ksys_ioctl+0x99/0xb0 fs/ioctl.c:701 __do_sys_ioctl fs/ioctl.c:708 [inline] __se_sys_ioctl fs/ioctl.c:706 [inline] __x64_sys_ioctl+0x78/0xb0 fs/ioctl.c:706 do_syscall_64+0xb0/0x460 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4497b9 RSP: 002b:00007f720c4bec68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f720c4bf6cc RCX: 00000000004497b9 RDX: 0000000020000040 RSI: 000200000000541c RDI: 0000000000000013 RBP: 000000000071bf58 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000005aa8 R14: 00000000006ecb48 R15: 00007f720c4bf700 The buggy address belongs to the page: page:ffffea0000004000 count:0 mapcount:-127 mapping:0000000000000000 index:0x0 flags: 0x0() raw: 0000000000000000 0000000000000000 0000000000000000 00000000ffffff80 raw: ffff88013fff9300 ffff88013fff9300 0000000000000008 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8800000fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff8800000fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ffff880000100000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff880000100080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff880000100100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ============================================================== Thanks, Kyungtae Kim On Thu, May 17, 2018 at 2:04 PM, Kyungtae Kim <kt0755@xxxxxxxxx> wrote: > We report the crash: > "KASAN: use-after-free Read in vgacon_invert_region" > > This crash was found in v4.17-rc3. Specifically, memory access (read > operation) is invalid, and it is detected by KASAN. > > C repro code: > https://kiwi.cs.purdue.edu/static/alexkkid-fuzzer/repro-ba6c1.c > kernel config: > https://kiwi.cs.purdue.edu/static/alexkkid-fuzzer/kernel-config-v4.17-rc3 > > Crash log: > ============================================================== > BUG: KASAN: use-after-free in vgacon_invert_region+0xf9/0x100 > drivers/video/console/vgacon.c:663 > Read of size 2 at addr ffff880000100000 by task syz-executor3/525 > > CPU: 0 PID: 525 Comm: syz-executor3 Not tainted 4.17.0-rc3 #3 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0xc7/0x138 lib/dump_stack.c:113 > print_address_description+0x78/0x290 mm/kasan/report.c:256 > kasan_report_error mm/kasan/report.c:354 [inline] > kasan_report+0x234/0x350 mm/kasan/report.c:412 > __asan_report_load2_noabort+0x19/0x20 mm/kasan/report.c:431 > vgacon_invert_region+0xf9/0x100 drivers/video/console/vgacon.c:663 > invert_screen+0x197/0x630 drivers/tty/vt/vt.c:461 > highlight drivers/tty/vt/selection.c:51 [inline] > set_selection+0x6b7/0xf60 drivers/tty/vt/selection.c:276 > tioclinux+0x126/0x410 drivers/tty/vt/vt.c:2691 > vt_ioctl+0x1036/0x2580 drivers/tty/vt/vt_ioctl.c:362 > tty_ioctl+0x288/0x14c0 drivers/tty/tty_io.c:2646 > vfs_ioctl fs/ioctl.c:46 [inline] > do_vfs_ioctl+0x191/0xfe0 fs/ioctl.c:686 > ksys_ioctl+0x99/0xb0 fs/ioctl.c:701 > __do_sys_ioctl fs/ioctl.c:708 [inline] > __se_sys_ioctl fs/ioctl.c:706 [inline] > __x64_sys_ioctl+0x78/0xb0 fs/ioctl.c:706 > do_syscall_64+0xb0/0x460 arch/x86/entry/common.c:287 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x4497b9 > RSP: 002b:00007f720c4bec68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 00007f720c4bf6cc RCX: 00000000004497b9 > RDX: 0000000020000040 RSI: 000200000000541c RDI: 0000000000000013 > RBP: 000000000071bf58 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff > R13: 0000000000005aa8 R14: 00000000006ecb48 R15: 00007f720c4bf700 > > The buggy address belongs to the page: > page:ffffea0000004000 count:0 mapcount:-127 mapping:0000000000000000 index:0x0 > flags: 0x0() > raw: 0000000000000000 0000000000000000 0000000000000000 00000000ffffff80 > raw: ffff88013fff9300 ffff88013fff9300 0000000000000008 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8800000fff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > ffff8800000fff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >>ffff880000100000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > ^ > ffff880000100080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > ffff880000100100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > ============================================================== > > > Thanks, > Kyungtae Kim _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
