bisecting fixing commit since eb575cd5d7f60241d016fdd13a9e86d962093c9b
building syzkaller on aba2b2fb3544d9e42991237c13d8cada421deda5
testing commit eb575cd5d7f60241d016fdd13a9e86d962093c9b
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: aed7c5adcf8f068558c4f66c5276595b3eea267135ad79d6f240f5072dc1c5c9
all runs: crashed: KASAN: use-after-free Read in __isofs_iget
testing current HEAD b172b44fcb1771e083aad806fa96f3f60e2ddfac
testing commit b172b44fcb1771e083aad806fa96f3f60e2ddfac
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 7b3d3c7e6ff401a2e4c7ce141e019d8e0a8e23e58858f624c07d8533774dee52
run #0: crashed: KASAN: use-after-free Read in __isofs_iget
run #1: crashed: KASAN: out-of-bounds Read in __isofs_iget
run #2: crashed: KASAN: out-of-bounds Read in __isofs_iget
run #3: crashed: KASAN: use-after-free Read in __isofs_iget
run #4: crashed: KASAN: use-after-free Read in __isofs_iget
run #5: crashed: KASAN: slab-out-of-bounds Read in __isofs_iget
run #6: crashed: KASAN: use-after-free Read in __isofs_iget
run #7: crashed: KASAN: use-after-free Read in __isofs_iget
run #8: crashed: KASAN: out-of-bounds Read in __isofs_iget
run #9: crashed: KASAN: use-after-free Read in __isofs_iget
revisions tested: 2, total time: 22m15.782670996s (build: 15m2.650628166s, test: 6m44.674541575s)
the crash still happens on HEAD
commit msg: Linux 4.19.206
crash: KASAN: use-after-free Read in __isofs_iget
IPv6: ADDRCONF(NETDEV_UP): wlan1: link is not ready
wlan1: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan1: Creating new IBSS network, BSSID 50:50:50:50:50:50
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
==================================================================
BUG: KASAN: use-after-free in isofs_read_inode fs/isofs/inode.c:1355 [inline]
BUG: KASAN: use-after-free in __isofs_iget+0x1c58/0x2010 fs/isofs/inode.c:1555
attempt to access beyond end of device
Read of size 1 at addr ffff8880816ff015 by task syz-executor.4/9974

CPU: 1 PID: 9974 Comm: syz-executor.4 Not tainted 4.19.206-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+0x17c/0x226 lib/dump_stack.c:118
 print_address_description.cold.6+0x9/0x211 mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:396
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
loop0: rw=524288, want=224, limit=136
 isofs_read_inode fs/isofs/inode.c:1355 [inline]
 __isofs_iget+0x1c58/0x2010 fs/isofs/inode.c:1555
attempt to access beyond end of device
 isofs_iget fs/isofs/isofs.h:134 [inline]
 isofs_export_iget.part.1+0x12/0x80 fs/isofs/export.c:29
 isofs_export_iget fs/isofs/export.c:170 [inline]
 isofs_fh_to_dentry+0xc7/0x110 fs/isofs/export.c:170
 exportfs_decode_fh+0x119/0x640 fs/exportfs/expfs.c:433
 do_handle_to_path fs/fhandle.c:152 [inline]
 handle_to_path fs/fhandle.c:207 [inline]
 do_handle_open+0x26c/0x5d0 fs/fhandle.c:223
 __do_sys_open_by_handle_at fs/fhandle.c:265 [inline]
 __se_sys_open_by_handle_at fs/fhandle.c:256 [inline]
 __x64_sys_open_by_handle_at+0x71/0xb0 fs/fhandle.c:256
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4665d9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
RSP: 002b:00007f4c63a20188 EFLAGS: 00000246 ORIG_RAX: 0000000000000130
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 00000000004665d9
RDX: 0000000000000000 RSI: 0000000020000040 RDI: 0000000000000005
RBP: 00000000004bfcb9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf80
R13: 00007ffd27e598df R14: 00007f4c63a20300 R15: 0000000000022000

The buggy address belongs to the page:
page:ffffea000205bfc0 count:0 mapcount:0 mapping:0000000000000000 index:0x1
flags: 0xfff00000000000()
raw: 00fff00000000000 ffffea000205c008 ffffea000205c148 0000000000000000
loop0: rw=524288, want=480, limit=136
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880816fef00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880816fef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880816ff000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                         ^
 ffff8880816ff080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880816ff100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================