================================================================== BUG: KASAN: use-after-free in fb_mode_is_equal+0x284/0x2f0 drivers/video/fbdev/core/modedb.c:924 Read of size 4 at addr ffff888026c47e1c by task syz-executor.2/13037 CPU: 1 PID: 13037 Comm: syz-executor.2 Not tainted 5.9.0-rc8-syzkaller #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x198/0x1fd lib/dump_stack.c:118 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383 __kasan_report mm/kasan/report.c:513 [inline] kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530 fb_mode_is_equal+0x284/0x2f0 drivers/video/fbdev/core/modedb.c:924 fbcon_mode_deleted+0x13d/0x1d0 drivers/video/fbdev/core/fbcon.c:2781 fb_set_var+0xa3f/0xce0 drivers/video/fbdev/core/fbmem.c:975 do_fb_ioctl+0x2f9/0x690 drivers/video/fbdev/core/fbmem.c:1104 fb_compat_ioctl+0x17c/0xc30 drivers/video/fbdev/core/fbmem.c:1311 __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842 do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline] __do_fast_syscall_32+0x60/0x90 arch/x86/entry/common.c:137 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c RIP: 0023:0xf7f9e549 Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 RSP: 002b:00000000f55980bc EFLAGS: 00000296 ORIG_RAX: 0000000000000036 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000004601 RDX: 0000000020000040 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 Allocated by task 10734: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 kasan_set_track mm/kasan/common.c:56 [inline] __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461 kmem_cache_alloc_trace+0x174/0x300 mm/slab.c:3554 kmalloc include/linux/slab.h:554 [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+0x58f/0xce0 drivers/video/fbdev/core/fbmem.c:1045 do_fb_ioctl+0x2f9/0x690 drivers/video/fbdev/core/fbmem.c:1104 fb_compat_ioctl+0x17c/0xc30 drivers/video/fbdev/core/fbmem.c:1311 __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842 do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline] __do_fast_syscall_32+0x60/0x90 arch/x86/entry/common.c:137 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c Freed by task 13021: kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422 __cache_free mm/slab.c:3422 [inline] kfree+0x10e/0x2b0 mm/slab.c:3760 fb_delete_videomode+0x3d2/0x570 drivers/video/fbdev/core/modedb.c:1104 fb_set_var+0xa4f/0xce0 drivers/video/fbdev/core/fbmem.c:978 do_fb_ioctl+0x2f9/0x690 drivers/video/fbdev/core/fbmem.c:1104 fb_compat_ioctl+0x17c/0xc30 drivers/video/fbdev/core/fbmem.c:1311 __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842 do_syscall_32_irqs_on arch/x86/entry/common.c:78 [inline] __do_fast_syscall_32+0x60/0x90 arch/x86/entry/common.c:137 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:160 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c The buggy address belongs to the object at ffff888026c47e00 which belongs to the cache kmalloc-96 of size 96 The buggy address is located 28 bytes inside of 96-byte region [ffff888026c47e00, ffff888026c47e60) The buggy address belongs to the page: page:000000001fdb3867 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26c47 flags: 0xfffe0000000200(slab) raw: 00fffe0000000200 ffffea0000764ac8 ffffea0000a61b08 ffff88802c840300 raw: 0000000000000000 ffff888026c47000 0000000100000020 ffff88801b406001 page dumped because: kasan: bad access detected page->mem_cgroup:ffff88801b406001 Memory state around the buggy address: ffff888026c47d00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff888026c47d80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc >ffff888026c47e00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ^ ffff888026c47e80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc ffff888026c47f00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ==================================================================