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BUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924
Read of size 4 at addr ffff88809e83269c by task syz-executor.0/27057

CPU: 0 PID: 27057 Comm: syz-executor.0 Not tainted 5.9.0-rc8-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+0x1d6/0x29e lib/dump_stack.c:118
 print_address_description+0x66/0x620 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report+0x132/0x1d0 mm/kasan/report.c:530
 fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924
 fbcon_mode_deleted+0xe6/0x170 drivers/video/fbdev/core/fbcon.c:2781
 fb_set_var+0x1d4/0xc50 drivers/video/fbdev/core/fbmem.c:975
 do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1104
 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: 0033:0x45de59
Code: 0d b4 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb22fb57c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000000e280 RCX: 000000000045de59
RDX: 0000000020000240 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 00007ffe0208cc2f R14: 00007fb22fb589c0 R15: 000000000118bf2c

Allocated by task 8286:
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc+0x100/0x130 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x1e4/0x2e0 mm/slab.c:3554
 kmalloc include/linux/slab.h:554 [inline]
 fb_add_videomode+0x6f9/0x810 drivers/video/fbdev/core/modedb.c:1073
 fb_set_var+0x685/0xc50 drivers/video/fbdev/core/fbmem.c:1045
 do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1104
 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

Freed by task 27046:
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track+0x3d/0x70 mm/kasan/common.c:56
 kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xdd/0x110 mm/kasan/common.c:422
 __cache_free mm/slab.c:3422 [inline]
 kfree+0x113/0x200 mm/slab.c:3760
 fb_delete_videomode+0x567/0x810 drivers/video/fbdev/core/modedb.c:1104
 fb_set_var+0x1e6/0xc50 drivers/video/fbdev/core/fbmem.c:978
 do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1104
 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

The buggy address belongs to the object at ffff88809e832680
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 28 bytes inside of
 96-byte region [ffff88809e832680, ffff88809e8326e0)
The buggy address belongs to the page:
page:00000000e4bde6ab refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88809e832300 pfn:0x9e832
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0001340848 ffffea0002814208 ffff8880aa440300
raw: ffff88809e832300 ffff88809e832000 000000010000001a 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809e832580: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88809e832600: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>ffff88809e832680: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                            ^
 ffff88809e832700: 00 00 00 00 00 00 00 00 00 02 fc fc fc fc fc fc
 ffff88809e832780: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
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