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BUG: KASAN: use-after-free in fb_mode_is_equal+0x21c/0x2e0 drivers/video/fbdev/core/modedb.c:981
Read of size 4 at addr ffff888095c1309c by task syz-executor.0/7914

CPU: 0 PID: 7914 Comm: syz-executor.0 Not tainted 5.2.0-rc4-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+0x113/0x167 lib/dump_stack.c:113
 print_address_description.cold.5+0x9/0x1ff mm/kasan/report.c:188
 __kasan_report.cold.6+0x1b/0x39 mm/kasan/report.c:317
 kasan_report+0x12/0x20 mm/kasan/common.c:614
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:131
 fb_mode_is_equal+0x21c/0x2e0 drivers/video/fbdev/core/modedb.c:981
 fbcon_mode_deleted+0xe6/0x140 drivers/video/fbdev/core/fbcon.c:3040
 fb_set_var+0x968/0xf40 drivers/video/fbdev/core/fbmem.c:970
 do_fb_ioctl+0x6ed/0x990 drivers/video/fbdev/core/fbmem.c:1120
 fb_ioctl+0xcb/0x150 drivers/video/fbdev/core/fbmem.c:1224
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:696
 ksys_ioctl+0x62/0x90 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718
 do_syscall_64+0xd0/0x530 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45a919
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:00007f80d38c4c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a919
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000011
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f80d38c56d4
R13: 00000000004c310d R14: 00000000004d8498 R15: 00000000ffffffff

Allocated by task 7645:
 save_stack+0x21/0x90 mm/kasan/common.c:71
 set_track mm/kasan/common.c:79 [inline]
 __kasan_kmalloc.constprop.12+0xc7/0xd0 mm/kasan/common.c:489
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:503
 kmem_cache_alloc_trace+0x154/0x740 mm/slab.c:3555
 kmalloc include/linux/slab.h:547 [inline]
 fb_add_videomode+0x22e/0x5c0 drivers/video/fbdev/core/modedb.c:1130
 fb_set_var+0x580/0xf40 drivers/video/fbdev/core/fbmem.c:1040
 do_fb_ioctl+0x6ed/0x990 drivers/video/fbdev/core/fbmem.c:1120
 fb_ioctl+0xcb/0x150 drivers/video/fbdev/core/fbmem.c:1224
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:696
 ksys_ioctl+0x62/0x90 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718
 do_syscall_64+0xd0/0x530 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 7818:
 save_stack+0x21/0x90 mm/kasan/common.c:71
 set_track mm/kasan/common.c:79 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:451
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:459
 __cache_free mm/slab.c:3432 [inline]
 kfree+0xcf/0x220 mm/slab.c:3755
 fb_delete_videomode+0x303/0x720 drivers/video/fbdev/core/modedb.c:1161
 fb_set_var+0x977/0xf40 drivers/video/fbdev/core/fbmem.c:973
 do_fb_ioctl+0x6ed/0x990 drivers/video/fbdev/core/fbmem.c:1120
 fb_ioctl+0xcb/0x150 drivers/video/fbdev/core/fbmem.c:1224
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:696
 ksys_ioctl+0x62/0x90 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:718
 do_syscall_64+0xd0/0x530 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888095c13080
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 28 bytes inside of
 96-byte region [ffff888095c13080, ffff888095c130e0)
The buggy address belongs to the page:
page:ffffea00025704c0 refcount:1 mapcount:0 mapping:ffff8880aa4004c0 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000260c5c8 ffffea0002373988 ffff8880aa4004c0
raw: 0000000000000000 ffff888095c13000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888095c12f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888095c13000: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff888095c13080: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                            ^
 ffff888095c13100: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff888095c13180: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
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