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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 ffff88809493499c by task syz-executor.1/9459

CPU: 0 PID: 9459 Comm: syz-executor.1 Not tainted 5.5.0-rc3-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_compat_ioctl+0x305/0xc50 drivers/video/fbdev/core/fbmem.c:1310
 __do_compat_sys_ioctl fs/compat_ioctl.c:214 [inline]
 __se_compat_sys_ioctl fs/compat_ioctl.c:142 [inline]
 __ia32_compat_sys_ioctl+0x233/0x610 fs/compat_ioctl.c:142
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7fc0a39
Code: 00 00 00 89 d3 5b 5e 5f 5d c3 b8 80 96 98 00 eb c4 8b 04 24 c3 8b 1c 24 c3 8b 34 24 c3 8b 3c 24 c3 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:00000000f7fbc0cc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 0000000000000013 RCX: 0000000000004601
RDX: 0000000020000000 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 9299:
 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_compat_ioctl+0x305/0xc50 drivers/video/fbdev/core/fbmem.c:1310
 __do_compat_sys_ioctl fs/compat_ioctl.c:214 [inline]
 __se_compat_sys_ioctl fs/compat_ioctl.c:142 [inline]
 __ia32_compat_sys_ioctl+0x233/0x610 fs/compat_ioctl.c:142
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Freed by task 9403:
 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_compat_ioctl+0x305/0xc50 drivers/video/fbdev/core/fbmem.c:1310
 __do_compat_sys_ioctl fs/compat_ioctl.c:214 [inline]
 __se_compat_sys_ioctl fs/compat_ioctl.c:142 [inline]
 __ia32_compat_sys_ioctl+0x233/0x610 fs/compat_ioctl.c:142
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

The buggy address belongs to the object at ffff888094934980
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 28 bytes inside of
 96-byte region [ffff888094934980, ffff8880949349e0)
The buggy address belongs to the page:
page:ffffea0002524d00 refcount:1 mapcount:0 mapping:ffff8880aa400540 index:0x0
raw: 00fffe0000000200 ffffea00025b82c8 ffffea0002548288 ffff8880aa400540
raw: 0000000000000000 ffff888094934000 0000000100000020 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888094934880: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff888094934900: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff888094934980: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
                            ^
 ffff888094934a00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff888094934a80: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
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