bisecting fixing commit since 830a059cbba6832c11fefc0894c7ec7a27f75734
building syzkaller on 6a81331a1d4c744da9204d02ec88d558f7eea9c9
testing commit 830a059cbba6832c11fefc0894c7ec7a27f75734
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 5d2a60cdfb3a4ab8f768521959c6620822a05ce2396a32257c4cf9939c8c097b
all runs: crashed: KASAN: out-of-bounds Read in ext4_xattr_set_entry
testing current HEAD b172b44fcb1771e083aad806fa96f3f60e2ddfac
testing commit b172b44fcb1771e083aad806fa96f3f60e2ddfac
compiler: gcc version 8.4.1 20210217 (GCC)
kernel signature: 23ca4a90f73528482d1e2a0796c74e177182f034f47e5a7851d182c62d57547e
all runs: crashed: KASAN: out-of-bounds Read in ext4_xattr_set_entry
revisions tested: 2, total time: 23m30.471198299s (build: 15m58.371016103s, test: 7m4.635544618s)
the crash still happens on HEAD
commit msg: Linux 4.19.206
crash: KASAN: out-of-bounds Read in ext4_xattr_set_entry
EXT4-fs error (device loop4): ext4_mb_generate_buddy:747: group 0, block bitmap and bg descriptor inconsistent: 50 vs 25 free clusters
EXT4-fs error (device loop3): ext4_mb_generate_buddy:747: group 0, block bitmap and bg descriptor inconsistent: 50 vs 25 free clusters
==================================================================
BUG: KASAN: out-of-bounds in memmove include/linux/string.h:392 [inline]
BUG: KASAN: out-of-bounds in ext4_xattr_set_entry+0x186c/0x3950 fs/ext4/xattr.c:1733
Read of size 18446744073709551600 at addr ffff88809d44f0d4 by task syz-executor.0/11159

CPU: 0 PID: 11159 Comm: syz-executor.0 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
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13c/0x1b0 mm/kasan/kasan.c:267
 memmove+0x23/0x50 mm/kasan/kasan.c:293
 memmove include/linux/string.h:392 [inline]
 ext4_xattr_set_entry+0x186c/0x3950 fs/ext4/xattr.c:1733
 ext4_xattr_ibody_inline_set+0x70/0x290 fs/ext4/xattr.c:2222
 ext4_destroy_inline_data_nolock+0x1d6/0x490 fs/ext4/inline.c:434
 ext4_convert_inline_data_nolock+0x136/0xc40 fs/ext4/inline.c:1207
 ext4_convert_inline_data+0x299/0x3c0 fs/ext4/inline.c:2027
 ext4_fallocate+0xdb/0x1920 fs/ext4/extents.c:4962
 vfs_fallocate+0x2b5/0x7c0 fs/open.c:308
 ksys_fallocate+0x3c/0x80 fs/open.c:331
 __do_sys_fallocate fs/open.c:339 [inline]
 __se_sys_fallocate fs/open.c:337 [inline]
 __x64_sys_fallocate+0x92/0xf0 fs/open.c:337
 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x466459
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
RSP: 002b:00007fd76a473188 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 000000000056c008 RCX: 0000000000466459
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00000000004bf9fb R08: 0000000000000000 R09: 0000000000000000
R10: 0000000010000101 R11: 0000000000000246 R12: 000000000056c008
R13: 00007ffc30a4146f R14: 00007fd76a473300 R15: 0000000000022000

The buggy address belongs to the page:
page:ffffea00027513c0 count:2 mapcount:0 mapping:ffff8880b1abdae0 index:0x8
flags: 0xfff00000001074(referenced|dirty|lru|active|private)
raw: 00fff00000001074 ffffea0002772f48 ffffea0002067908 ffff8880b1abdae0
raw: 0000000000000008 ffff8880816325e8 00000002ffffffff ffff88823b2d4900
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff88823b2d4900

Memory state around the buggy address:
 ffff88809d44ef80: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc
 ffff88809d44f000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88809d44f080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                                                 ^
 ffff88809d44f100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88809d44f180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================