bisecting fixing commit since 030194a5b292bb7613407668d85af0b987bb9839
building syzkaller on 4a003785c5484e99127a20e069a5edddcb8c24d5
testing commit 030194a5b292bb7613407668d85af0b987bb9839 with gcc (GCC) 8.4.1 20210217
kernel signature: 6b5d6307b4930896803388086b681c004baef8482679509957e3532a3c67216b
all runs: crashed: KASAN: use-after-free Read in search_by_entry_key
testing current HEAD 9a2dc0e6c531d595bcdf2c66d0be131679bd02df
testing commit 9a2dc0e6c531d595bcdf2c66d0be131679bd02df with gcc (GCC) 8.4.1 20210217
kernel signature: 45c1313b934dd5eba1fdb251208bad315635d86dc49ca3e018d5c7cc001be708
run #0: crashed: KASAN: use-after-free Read in search_by_entry_key
run #1: crashed: KASAN: use-after-free Read in search_by_entry_key
run #2: crashed: KASAN: use-after-free Read in search_by_entry_key
run #3: crashed: KASAN: use-after-free Read in search_by_entry_key
run #4: crashed: KASAN: use-after-free Read in search_by_entry_key
run #5: crashed: KASAN: use-after-free Read in search_by_entry_key
run #6: crashed: KASAN: use-after-free Read in search_by_entry_key
run #7: crashed: KASAN: use-after-free Read in search_by_entry_key
run #8: crashed: KASAN: out-of-bounds Read in search_by_entry_key
run #9: crashed: KASAN: use-after-free Read in search_by_entry_key
revisions tested: 2, total time: 29m27.763115453s (build: 22m9.81692909s, test: 6m51.893737571s)
the crash still happens on HEAD
commit msg: Linux 4.19.194
crash: KASAN: use-after-free Read in search_by_entry_key
IPv6: ADDRCONF(NETDEV_CHANGE): wlan1: link becomes ready
REISERFS (device loop3): checking transaction log (loop3)
REISERFS (device loop3): Using rupasov hash to sort names
==================================================================
REISERFS (device loop1): found reiserfs format "3.5" with non-standard journal
BUG: KASAN: use-after-free in bin_search_in_dir_item fs/reiserfs/namei.c:40 [inline]
BUG: KASAN: use-after-free in search_by_entry_key+0xbf9/0xf30 fs/reiserfs/namei.c:164
Read of size 4 at addr ffff888080efa004 by task syz-executor.3/9944

CPU: 0 PID: 9944 Comm: syz-executor.3 Not tainted 4.19.194-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
REISERFS (device loop1): using ordered data mode
 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_load_n_noabort+0xf/0x20 mm/kasan/report.c:443
 bin_search_in_dir_item fs/reiserfs/namei.c:40 [inline]
 search_by_entry_key+0xbf9/0xf30 fs/reiserfs/namei.c:164
 reiserfs_find_entry.part.5+0x15a/0x17f0 fs/reiserfs/namei.c:321
 reiserfs_find_entry fs/reiserfs/namei.c:367 [inline]
 reiserfs_lookup+0x216/0x420 fs/reiserfs/namei.c:367
reiserfs: using flush barriers
 __lookup_slow+0x20d/0x3f0 fs/namei.c:1672
 lookup_one_len+0x132/0x160 fs/namei.c:2544
REISERFS (device loop1): journal params: device loop1, size 15748, journal first block 18, max trans len 1024, max batch 900, max commit age 0, max trans age 30
 reiserfs_lookup_privroot+0x94/0x270 fs/reiserfs/xattr.c:970
 reiserfs_fill_super+0x1139/0x26b0 fs/reiserfs/super.c:2197
 mount_bdev+0x26f/0x330 fs/super.c:1158
REISERFS (device loop1): checking transaction log (loop1)
 get_super_block+0x10/0x20 fs/reiserfs/super.c:2609
 mount_fs+0x7f/0x2b0 fs/super.c:1261
 vfs_kern_mount.part.11+0x58/0x3d0 fs/namespace.c:961
 vfs_kern_mount fs/namespace.c:951 [inline]
 do_new_mount fs/namespace.c:2469 [inline]
 do_mount+0x376/0x2710 fs/namespace.c:2799
REISERFS (device loop1): Using rupasov hash to sort names
 ksys_mount+0xb1/0xd0 fs/namespace.c:3015
 __do_sys_mount fs/namespace.c:3029 [inline]
 __se_sys_mount fs/namespace.c:3026 [inline]
 __x64_sys_mount+0xb9/0x150 fs/namespace.c:3026
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x46748a
Code: 48 c7 c2 bc ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb d2 e8 b8 04 00 00 0f 1f 84 00 00 00 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1a6f5ddfa8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000020000040 RCX: 000000000046748a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007f1a6f5de000
RBP: 00007f1a6f5de040 R08: 00007f1a6f5de040 R09: 0000000020000000
R10: 0000000000208403 R11: 0000000000000246 R12: 0000000020000000
R13: 0000000020000100 R14: 00007f1a6f5de000 R15: 0000000020011500

The buggy address belongs to the page:
page:ffffea000203be80 count:0 mapcount:0 mapping:0000000000000000 index:0x1
flags: 0xfff00000000000()
raw: 00fff00000000000 ffffea00020578c8 ffffea000205a988 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888080ef9f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888080ef9f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888080efa000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888080efa080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888080efa100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
REISERFS (device loop2): found reiserfs format "3.5" with non-standard journal
wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50
wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50