KASAN: use-after-free Read in ext4_xattr_set

KASAN: use-after-free Read in ext4_xattr_set_entry (4)
Status: upstream: reported C repro on 2021/01/30 11:05
Reported-by: syzbot+4cb1e27475bf90a9b926@syzkaller.appspotmail.com
First crash: 33d, last: 33d

Cause bisection: failed (bisect log)

similar bugs (11):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
linux-4.14	KASAN: use-after-free Read in ext4_xattr_set_entry (3)	C			1	3d02h	123d	0/1	upstream: reported C repro on 2020/10/28 15:08
android-414	KASAN: use-after-free Read in ext4_xattr_set_entry (2)				6	486d	542d	0/1	auto-closed as invalid on 2020/02/28 13:35
linux-4.14	KASAN: use-after-free Read in ext4_xattr_set_entry (2)				1	342d	342d	0/1	auto-closed as invalid on 2020/07/21 03:20
linux-4.19	KASAN: use-after-free Read in ext4_xattr_set_entry (2)	C			5	6d01h	262d	0/1	upstream: reported C repro on 2020/06/11 12:57
upstream	KASAN: use-after-free Read in ext4_xattr_set_entry				1	947d	947d	0/21	closed as invalid on 2018/07/29 11:55
android-414	KASAN: use-after-free Read in ext4_xattr_set_entry				4	793d	686d	0/1	auto-closed as invalid on 2019/06/26 01:15
upstream	KASAN: use-after-free Read in ext4_xattr_set_entry (3)				4	238d	356d	0/21	auto-closed as invalid on 2020/11/02 08:32
linux-4.19	KASAN: use-after-free Read in ext4_xattr_set_entry	syz		done	10	365d	614d	1/1	fixed on 2020/03/30 09:03
upstream	KASAN: use-after-free Read in ext4_xattr_set_entry (2)	C	done		19	440d	849d	16/21	fixed on 2020/02/14 01:19
android-54	KASAN: use-after-free Read in ext4_xattr_set_entry				6	206d	387d	0/1	auto-closed as invalid on 2020/12/04 21:44
linux-4.14	KASAN: use-after-free Read in ext4_xattr_set_entry	C		done	9	394d	486d	1/1	fixed on 2020/03/01 21:06

Sample crash report:

==================================================================
BUG: KASAN: use-after-free in ext4_xattr_set_entry+0x3151/0x3780 fs/ext4/xattr.c:1586
Read of size 4 at addr ffff888030c00004 by task syz-executor392/11280

CPU: 0 PID: 11280 Comm: syz-executor392 Not tainted 5.11.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:230
 __kasan_report mm/kasan/report.c:396 [inline]
 kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413
 ext4_xattr_set_entry+0x3151/0x3780 fs/ext4/xattr.c:1586
 ext4_xattr_ibody_set+0x78/0x2b0 fs/ext4/xattr.c:2224
 ext4_xattr_set_handle+0x8f4/0x13e0 fs/ext4/xattr.c:2380
 ext4_xattr_set+0x13a/0x340 fs/ext4/xattr.c:2493
 __vfs_setxattr+0x10e/0x170 fs/xattr.c:177
 __vfs_setxattr_noperm+0x11a/0x4c0 fs/xattr.c:208
 __vfs_setxattr_locked+0x1bf/0x250 fs/xattr.c:266
 vfs_setxattr+0x135/0x320 fs/xattr.c:291
 setxattr+0x1ff/0x290 fs/xattr.c:553
 path_setxattr+0x170/0x190 fs/xattr.c:572
 __do_sys_setxattr fs/xattr.c:587 [inline]
 __se_sys_setxattr fs/xattr.c:583 [inline]
 __x64_sys_setxattr+0xc0/0x160 fs/xattr.c:583
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x445589
Code: e8 4c b3 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 0f 83 0b cc fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffdf5f9b28 EFLAGS: 00000246 ORIG_RAX: 00000000000000bc
RAX: ffffffffffffffda RBX: 0000000000000016 RCX: 0000000000445589
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000020000100
RBP: 0000000001a18c30 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000073d
R13: 00007fffdf5f9ba0 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:00000000f7ed6945 refcount:0 mapcount:-128 mapping:0000000000000000 index:0x1 pfn:0x30c00
flags: 0xfff00000000000()
raw: 00fff00000000000 ffffea0000c56508 ffffea0000c17d88 0000000000000000
raw: 0000000000000001 0000000000000001 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888030bfff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888030bfff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888030c00000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff888030c00080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888030c00100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-kasan-gce-root	2021/01/26 10:55	upstream	f8ad8187	52e37319	.config	log	report	syz	C		KASAN: use-after-free Read in ext4_xattr_set_entry