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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 ffff88809533c59c by task syz-executor.1/16241

CPU: 0 PID: 16241 Comm: syz-executor.1 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+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_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1181
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/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:00007f1dfea1bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000000e280 RCX: 000000000045de59
RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003
RBP: 000000000118bf60 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bf2c
R13: 000000000169fb7f R14: 00007f1dfea1c9c0 R15: 000000000118bf2c

Allocated by task 18930:
 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_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1181
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 16211:
 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_ioctl+0xe7/0x150 drivers/video/fbdev/core/fbmem.c:1181
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff88809533c580
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 28 bytes inside of
 96-byte region [ffff88809533c580, ffff88809533c5e0)
The buggy address belongs to the page:
page:00000000ed81a9f0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x9533c
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00028a9e88 ffffea0002a486c8 ffff8880aa040300
raw: 0000000000000000 ffff88809533c000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809533c480: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
 ffff88809533c500: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
>ffff88809533c580: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                            ^
 ffff88809533c600: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
 ffff88809533c680: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
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