KASAN: use-after-free Read in ext4_xattr_set

KASAN: use-after-free Read in ext4_xattr_set_entry
Status: public: reported on 2019/04/14 00:02
Reported-by: syzbot+14d28d8eae5ee1bd6f88@syzkaller.appspotmail.com
First crash: 234d, last: 171d

similar bugs (2):
Kernel	Title	Repro	Bisected	Count	Last	Reported	Patched	Status
upstream	KASAN: use-after-free Read in ext4_xattr_set_entry			1	324d	324d	0/13	closed as invalid on 2018/07/29 11:55
upstream	KASAN: use-after-free Read in ext4_xattr_set_entry (2)			10	49d	227d	0/13	upstream: reported on 2018/11/02 15:39

Sample crash report:

EXT4-fs error (device sda1): ext4_xattr_set_entry:1602: inode #16690: comm syz-fuzzer: corrupted xattr entries
EXT4-fs error (device sda1): ext4_xattr_set_entry:1602: inode #16690: comm syz-fuzzer: corrupted xattr entries
EXT4-fs error (device sda1): ext4_xattr_set_entry:1602: inode #16690: comm syz-fuzzer: corrupted xattr entries
EXT4-fs error (device sda1): ext4_xattr_set_entry:1602: inode #16690: comm syz-fuzzer: corrupted xattr entries
==================================================================
BUG: KASAN: use-after-free in ext4_xattr_set_entry+0x24c7/0x2e10 fs/ext4/xattr.c:1599
Read of size 4 at addr ffff88019ad5c083 by task syz-fuzzer/11081

CPU: 1 PID: 11081 Comm: syz-fuzzer Not tainted 4.14.78+ #26
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x11b lib/dump_stack.c:53
 print_address_description+0x60/0x22b mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report.cold.6+0x11b/0x2dd mm/kasan/report.c:409
 ext4_xattr_set_entry+0x24c7/0x2e10 fs/ext4/xattr.c:1599
 ext4_xattr_ibody_set+0x73/0x280 fs/ext4/xattr.c:2239
 ext4_xattr_set_handle+0x6a6/0xd90 fs/ext4/xattr.c:2393
 ext4_initxattrs+0xb8/0x110 fs/ext4/xattr_security.c:43
 security_inode_init_security+0x228/0x310 security/security.c:493
 __ext4_new_inode+0x3473/0x48e0 fs/ext4/ialloc.c:1166
 ext4_mkdir+0x234/0xb40 fs/ext4/namei.c:2624
 vfs_mkdir2+0x3cb/0x640 fs/namei.c:3836
 SYSC_mkdirat fs/namei.c:3865 [inline]
 SyS_mkdirat+0x126/0x220 fs/namei.c:3849
 do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x47fc44
RSP: 002b:000000c4240f9858 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000047fc44
RDX: 00000000000001c0 RSI: 000000c4206e29c0 RDI: ffffffffffffff9c
RBP: 000000c4240f98b8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb29926a000
R13: 0000000000000020 R14: 0000000000000013 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea00066b5700 count:0 mapcount:-127 mapping:          (null) index:0x1
flags: 0x4000000000000000()
raw: 4000000000000000 0000000000000000 0000000000000001 00000000ffffff80
raw: ffffea0006b5a520 ffffea00066bf820 0000000000000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88019ad5bf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88019ad5c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88019ad5c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88019ad5c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88019ad5c180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

All crashes (4):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Maintainers
ci-android-414-kasan-gce-root	2018/10/25 18:06	android-4.14	4ed22187	a8292de9	.config	log	report	adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu
ci-android-414-kasan-gce-root	2018/12/28 01:14	android-4.14	815e34f8	af317504	.config	log	report	adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu
ci-android-414-kasan-gce-root	2018/12/11 20:44	android-4.14	e525d2cf	7795ae03	.config	log	report	adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu
ci-android-414-kasan-gce-root	2018/11/02 21:33	android-4.14	4ed22187	8bd6bd63	.config	log	report	adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, tytso@mit.edu