bisecting fixing commit since 5b7a52cd2eef952cee8a72512ef370bcdef46636
building syzkaller on 96e03c1c31a7f2e7f80b2d8b9f3df117df5030d1
testing commit 5b7a52cd2eef952cee8a72512ef370bcdef46636 with gcc (GCC) 8.4.1 20210217
kernel signature: c741ae01946b890d81d58fab436e6456587fa5ad14ac79b95a569fcfc9daa2c5
run #0: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #1: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #2: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #3: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #4: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #5: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #6: crashed: KASAN: out-of-bounds Read in ext4_xattr_set_entry
run #7: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #8: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #9: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #10: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #11: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #12: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #13: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #14: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #15: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #16: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #17: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #18: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
run #19: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
testing current HEAD 3242aa3a635c0958671ee1e4b0958dcc7c4e5c79
testing commit 3242aa3a635c0958671ee1e4b0958dcc7c4e5c79 with gcc (GCC) 8.4.1 20210217
kernel signature: 2a13d3a4c43c4d7b5ea84d030985e1fd78c337023a235e36e78028f67a50d9a8
all runs: crashed: KASAN: use-after-free Read in ext4_xattr_set_entry
revisions tested: 2, total time: 23m49.638248663s (build: 14m19.039007043s, test: 8m36.458494053s)
the crash still happens on HEAD
commit msg: Linux 4.14.222
crash: KASAN: use-after-free Read in ext4_xattr_set_entry
EXT4-fs (sda1): Unrecognized mount option "fscontext=user_u" or missing value
EXT4-fs (sda1): Unrecognized mount option "fscontext=user_u" or missing value
EXT4-fs (sda1): Unrecognized mount option "fscontext=user_u" or missing value
==================================================================
BUG: KASAN: use-after-free in ext4_xattr_set_entry+0x2713/0x3790 fs/ext4/xattr.c:1603
Read of size 4 at addr ffff8881c9af1004 by task syz-executor.0/13873

CPU: 1 PID: 13873 Comm: syz-executor.0 Not tainted 4.14.222-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x14b/0x1e7 lib/dump_stack.c:58
 print_address_description.cold.6+0x9/0x1ca mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold.7+0x11a/0x2d3 mm/kasan/report.c:393
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:429
 ext4_xattr_set_entry+0x2713/0x3790 fs/ext4/xattr.c:1603
 ext4_xattr_ibody_set+0x70/0x290 fs/ext4/xattr.c:2242
 ext4_xattr_set_handle+0x57c/0xc40 fs/ext4/xattr.c:2398
 ext4_xattr_set+0x1b4/0x2e0 fs/ext4/xattr.c:2510
 ext4_xattr_trusted_set+0x1e/0x20 fs/ext4/xattr_trusted.c:37
 __vfs_setxattr+0xd1/0x130 fs/xattr.c:150
 __vfs_setxattr_noperm+0xe9/0x380 fs/xattr.c:181
 __vfs_setxattr_locked+0x182/0x200 fs/xattr.c:239
 vfs_setxattr+0xf5/0x260 fs/xattr.c:256
 setxattr+0x1a0/0x250 fs/xattr.c:523
 path_setxattr+0x130/0x150 fs/xattr.c:542
 SYSC_setxattr fs/xattr.c:557 [inline]
 SyS_setxattr+0xf/0x20 fs/xattr.c:553
 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x465849
RSP: 002b:00007f72a644f188 EFLAGS: 00000246 ORIG_RAX: 00000000000000bc
RAX: ffffffffffffffda RBX: 000000000055bfa8 RCX: 0000000000465849
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000020000100
RBP: 00000000004af675 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bfa8
R13: 00007ffe73860c0f R14: 00007f72a644f300 R15: 0000000000022000

The buggy address belongs to the page:
page:ffffea000726bc40 count:0 mapcount:0 mapping:          (null) index:0x1
flags: 0x17ff00000000000()
raw: 017ff00000000000 0000000000000000 0000000000000001 00000000ffffffff
raw: ffffea0007265620 ffffea0007268020 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c9af0f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881c9af0f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881c9af1000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8881c9af1080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881c9af1100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================