On Sat, 07 Dec 2019 02:05:08 -0800 > Hello, > > syzbot found the following crash on: > > HEAD commit: 7ada90eb Merge tag 'drm-next-2019-12-06' of git://anongit... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=16997c82e00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=f07a23020fd7d21a > dashboard link: https://syzkaller.appspot.com/bug?extid=f11cda116c57db68c227 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > Unfortunately, I don't have any reproducer for this crash yet. > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+f11cda116c57db68c227@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================================================== > BUG: KASAN: use-after-free in fb_mode_is_equal+0x297/0x300 > drivers/video/fbdev/core/modedb.c:924 > Read of size 4 at addr ffff8880992d5d9c by task syz-executor.0/32283 > > CPU: 0 PID: 32283 Comm: syz-executor.0 Not tainted 5.4.0-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > Google 01/01/2011 > Call Trace: > __dump_stack lib/dump_stack.c:77 [inline] > dump_stack+0x197/0x210 lib/dump_stack.c:118 > print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374 > __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506 > kasan_report+0x12/0x20 mm/kasan/common.c:639 > __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:134 > fb_mode_is_equal+0x297/0x300 drivers/video/fbdev/core/modedb.c:924 > fbcon_mode_deleted+0x12c/0x190 drivers/video/fbdev/core/fbcon.c:3060 > fb_set_var+0xab9/0xdd0 drivers/video/fbdev/core/fbmem.c:971 > do_fb_ioctl+0x390/0x7d0 drivers/video/fbdev/core/fbmem.c:1104 > fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180 > vfs_ioctl fs/ioctl.c:47 [inline] > file_ioctl fs/ioctl.c:545 [inline] > do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 > ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 > __do_sys_ioctl fs/ioctl.c:756 [inline] > __se_sys_ioctl fs/ioctl.c:754 [inline] > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 > do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > RIP: 0033:0x45a6f9 > Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 > RSP: 002b:00007f7aefd54c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a6f9 > RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 > RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 00007f7aefd556d4 > R13: 00000000004c2ef7 R14: 00000000004d8138 R15: 00000000ffffffff > > Allocated by task 9205: > save_stack+0x23/0x90 mm/kasan/common.c:72 > set_track mm/kasan/common.c:80 [inline] > __kasan_kmalloc mm/kasan/common.c:513 [inline] > __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:486 > kasan_kmalloc+0x9/0x10 mm/kasan/common.c:527 > kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3551 > kmalloc include/linux/slab.h:556 [inline] > fb_add_videomode drivers/video/fbdev/core/modedb.c:1073 [inline] > fb_add_videomode+0x2fb/0x610 drivers/video/fbdev/core/modedb.c:1057 > fb_set_var+0x5ef/0xdd0 drivers/video/fbdev/core/fbmem.c:1041 > do_fb_ioctl+0x390/0x7d0 drivers/video/fbdev/core/fbmem.c:1104 > fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180 > vfs_ioctl fs/ioctl.c:47 [inline] > file_ioctl fs/ioctl.c:545 [inline] > do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 > ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 > __do_sys_ioctl fs/ioctl.c:756 [inline] > __se_sys_ioctl fs/ioctl.c:754 [inline] > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 > do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Freed by task 32276: > save_stack+0x23/0x90 mm/kasan/common.c:72 > set_track mm/kasan/common.c:80 [inline] > kasan_set_free_info mm/kasan/common.c:335 [inline] > __kasan_slab_free+0x102/0x150 mm/kasan/common.c:474 > kasan_slab_free+0xe/0x10 mm/kasan/common.c:483 > __cache_free mm/slab.c:3426 [inline] > kfree+0x10a/0x2c0 mm/slab.c:3757 > fb_delete_videomode+0x3fa/0x540 drivers/video/fbdev/core/modedb.c:1104 > fb_set_var+0xac8/0xdd0 drivers/video/fbdev/core/fbmem.c:974 > do_fb_ioctl+0x390/0x7d0 drivers/video/fbdev/core/fbmem.c:1104 > fb_ioctl+0xe6/0x130 drivers/video/fbdev/core/fbmem.c:1180 > vfs_ioctl fs/ioctl.c:47 [inline] > file_ioctl fs/ioctl.c:545 [inline] > do_vfs_ioctl+0x977/0x14e0 fs/ioctl.c:732 > ksys_ioctl+0xab/0xd0 fs/ioctl.c:749 > __do_sys_ioctl fs/ioctl.c:756 [inline] > __se_sys_ioctl fs/ioctl.c:754 [inline] > __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 > do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > The buggy address belongs to the object at ffff8880992d5d80 > which belongs to the cache kmalloc-96 of size 96 > The buggy address is located 28 bytes inside of > 96-byte region [ffff8880992d5d80, ffff8880992d5de0) > The buggy address belongs to the page: > page:ffffea000264b540 refcount:1 mapcount:0 mapping:ffff8880aa400540 > index:0x0 > raw: 00fffe0000000200 ffffea00025470c8 ffffea0002992508 ffff8880aa400540 > raw: 0000000000000000 ffff8880992d5000 0000000100000020 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: > ffff8880992d5c80: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc > ffff8880992d5d00: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc > > ffff8880992d5d80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > ^ > ffff8880992d5e00: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc > ffff8880992d5e80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc > ================================================================== Reset mode that will be deleted to avoid UAF. --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -3058,6 +3058,7 @@ int fbcon_mode_deleted(struct fb_info *i if (!p || !p->mode) continue; if (fb_mode_is_equal(p->mode, mode)) { + p->mode = NULL; found = 1; break; } _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
