Date:   Wed, 23 Feb 2022 11:17:07 +0000
From:   "Zhang, Qiang1" <qiang1.zhang@...el.com>
To:     syzbot <syzbot+348b571beb5eeb70a582@...kaller.appspotmail.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "rafael@...nel.org" <rafael@...nel.org>,
        "syzkaller-bugs@...glegroups.com" <syzkaller-bugs@...glegroups.com>,
        "balbi@...nel.org" <balbi@...nel.org>,
        "stern@...land.harvard.edu" <stern@...land.harvard.edu>
Subject: RE: [syzbot] KASAN: use-after-free Read in dev_uevent


syzbot has found a reproducer for the following issue on:

HEAD commit:    4f12b742eb2b Merge tag 'nfs-for-5.17-3' of git://git.linux..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=110a6df2700000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f6a069ed94a1ed1d
dashboard link: https://syzkaller.appspot.com/bug?extid=348b571beb5eeb70a582
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12377296700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+348b571beb5eeb70a582@...kaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in dev_uevent+0x712/0x780 drivers/base/core.c:2320 Read of size 8 at addr ffff88802b934098 by task udevd/3689

CPU: 2 PID: 3689 Comm: udevd Not tainted 5.17.0-rc4-syzkaller-00229-g4f12b742eb2b #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014 Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0x8d/0x303 mm/kasan/report.c:255  __kasan_report mm/kasan/report.c:442 [inline]  kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
 dev_uevent+0x712/0x780 drivers/base/core.c:2320
 uevent_show+0x1b8/0x380 drivers/base/core.c:2391
 dev_attr_show+0x4b/0x90 drivers/base/core.c:2094
 sysfs_kf_seq_show+0x219/0x3d0 fs/sysfs/file.c:59
 seq_read_iter+0x4f5/0x1280 fs/seq_file.c:230
 kernfs_fop_read_iter+0x514/0x6f0 fs/kernfs/file.c:241  call_read_iter include/linux/fs.h:2068 [inline]
 new_sync_read+0x429/0x6e0 fs/read_write.c:400
 vfs_read+0x35c/0x600 fs/read_write.c:481
 ksys_read+0x12d/0x250 fs/read_write.c:619
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80  entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f964cc558fe
Code: c0 e9 e6 fe ff ff 50 48 8d 3d 0e c7 09 00 e8 c9 cf 01 00 66 0f 1f 84 00 00 00 00 00 64 8b 04 25 18 00 00 00 85 c0 75 14 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 66 0f 1f 84 00 00 00 00 00 48 83 ec 28
RSP: 002b:00007ffc0133d258 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 000056497b21a140 RCX: 00007f964cc558fe
RDX: 0000000000001000 RSI: 000056497b218650 RDI: 0000000000000008
RBP: 00007f964cd22380 R08: 0000000000000008 R09: 00007f964cd25a60
R10: 0000000000000008 R11: 0000000000000246 R12: 000056497b21a140
R13: 0000000000000d68 R14: 00007f964cd21780 R15: 0000000000000d68  </TASK>

Cc: Alan Stern 
       Felipe Balbi

Hello syzbot, Please try it:

From 574d45ff924e2d2f9b9f5cc3e846f8004498a811 Mon Sep 17 00:00:00 2001
From: Zqiang <qiang1.zhang@...el.com>
Date: Wed, 23 Feb 2022 18:18:22 +0800
Subject: [PATCH] driver core: Fix use-after-free in dev_uevent()

In dev_uevent(), if the "dev->driver" is valid, the "dev->driver->name"
be accessed, there may be a window period between these two operations.
in this window period if the "dev->driver" is set to null
(in usb_gadget_unregister_driver function), when the "dev->driver->name"
is accessed again, invalid address will be accessed. fix it by checking
"dev->driver" again.

Signed-off-by: Zqiang <qiang1.zhang@...el.com>
---
 drivers/base/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 3d6430eb0c6a..a45b927ee76e 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2317,7 +2317,7 @@ static int dev_uevent(struct kobject *kobj, struct kobj_uevent_env *env)
                add_uevent_var(env, "DEVTYPE=%s", dev->type->name);

        if (dev->driver)
-               add_uevent_var(env, "DRIVER=%s", dev->driver->name);
+               add_uevent_var(env, "DRIVER=%s", dev_driver_string(dev));

        /* Add common DT information about the device */
        of_device_uevent(dev, env);
--
2.25.1

Thanks,
Zqiang

Allocated by task 4316:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38  kasan_set_track mm/kasan/common.c:45 [inline]  set_alloc_info mm/kasan/common.c:436 [inline]  ____kasan_kmalloc mm/kasan/common.c:515 [inline]  ____kasan_kmalloc mm/kasan/common.c:474 [inline]
 __kasan_kmalloc+0xa6/0xd0 mm/kasan/common.c:524  kasan_kmalloc include/linux/kasan.h:270 [inline]
 kmem_cache_alloc_trace+0x1ea/0x4a0 mm/slab.c:3567  kmalloc include/linux/slab.h:581 [inline]  kzalloc include/linux/slab.h:715 [inline]  dev_new drivers/usb/gadget/legacy/raw_gadget.c:183 [inline]
 raw_open+0x8d/0x4c0 drivers/usb/gadget/legacy/raw_gadget.c:373
 misc_open+0x372/0x4a0 drivers/char/misc.c:141
 chrdev_open+0x266/0x770 fs/char_dev.c:414
 do_dentry_open+0x4b9/0x1250 fs/open.c:824  do_open fs/namei.c:3476 [inline]
 path_openat+0x1c9e/0x2940 fs/namei.c:3609
 do_filp_open+0x1aa/0x400 fs/namei.c:3636
 do_sys_openat2+0x16d/0x4d0 fs/open.c:1214  do_sys_open fs/open.c:1230 [inline]  __do_sys_openat fs/open.c:1246 [inline]  __se_sys_openat fs/open.c:1241 [inline]
 __x64_sys_openat+0x13f/0x1f0 fs/open.c:1241
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80  entry_SYSCALL_64_after_hwframe+0x44/0xae

Freed by task 4315:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track+0x21/0x30 mm/kasan/common.c:45
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370  ____kasan_slab_free mm/kasan/common.c:366 [inline]
 ____kasan_slab_free+0xff/0x140 mm/kasan/common.c:328  kasan_slab_free include/linux/kasan.h:236 [inline]  __cache_free mm/slab.c:3437 [inline]
 kfree+0xf8/0x2b0 mm/slab.c:3794
 kref_put include/linux/kref.h:65 [inline]
 raw_release+0x218/0x290 drivers/usb/gadget/legacy/raw_gadget.c:412
 __fput+0x286/0x9f0 fs/file_table.c:317
 task_work_run+0xdd/0x1a0 kernel/task_work.c:164  tracehook_notify_resume include/linux/tracehook.h:188 [inline]  exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:207  __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86  entry_SYSCALL_64_after_hwframe+0x44/0xae

The buggy address belongs to the object at ffff88802b934000  which belongs to the cache kmalloc-4k of size 4096 The buggy address is located 152 bytes inside of  4096-byte region [ffff88802b934000, ffff88802b935000) The buggy address belongs to the page:
page:ffffea0000ae4d00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2b934
head:ffffea0000ae4d00 order:1 compound_mapcount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 ffffea00008be908 ffffea0000612d08 ffff888010c40900
raw: 0000000000000000 ffff88802b934000 0000000100000001 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 1, migratetype Unmovable, gfp_mask 0x2420c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_COMP|__GFP_THISNODE), pid 4316, ts 254636955499, free_ts 240714313612  prep_new_page mm/page_alloc.c:2434 [inline]
 get_page_from_freelist+0xa72/0x2f50 mm/page_alloc.c:4165
 __alloc_pages_slowpath.constprop.0+0x2eb/0x20d0 mm/page_alloc.c:4934
 __alloc_pages+0x412/0x500 mm/page_alloc.c:5402  __alloc_pages_node include/linux/gfp.h:572 [inline]  kmem_getpages mm/slab.c:1378 [inline]
 cache_grow_begin+0x75/0x390 mm/slab.c:2584
 cache_alloc_refill+0x27f/0x380 mm/slab.c:2957  ____cache_alloc mm/slab.c:3040 [inline]  ____cache_alloc mm/slab.c:3023 [inline]  __do_cache_alloc mm/slab.c:3267 [inline]  slab_alloc mm/slab.c:3308 [inline]
 kmem_cache_alloc_trace+0x380/0x4a0 mm/slab.c:3565  kmalloc include/linux/slab.h:581 [inline]  kzalloc include/linux/slab.h:715 [inline]  dev_new drivers/usb/gadget/legacy/raw_gadget.c:183 [inline]
 raw_open+0x8d/0x4c0 drivers/usb/gadget/legacy/raw_gadget.c:373
 misc_open+0x372/0x4a0 drivers/char/misc.c:141
 chrdev_open+0x266/0x770 fs/char_dev.c:414
 do_dentry_open+0x4b9/0x1250 fs/open.c:824  do_open fs/namei.c:3476 [inline]
 path_openat+0x1c9e/0x2940 fs/namei.c:3609
 do_filp_open+0x1aa/0x400 fs/namei.c:3636
 do_sys_openat2+0x16d/0x4d0 fs/open.c:1214  do_sys_open fs/open.c:1230 [inline]  __do_sys_openat fs/open.c:1246 [inline]  __se_sys_openat fs/open.c:1241 [inline]
 __x64_sys_openat+0x13f/0x1f0 fs/open.c:1241
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80  entry_SYSCALL_64_after_hwframe+0x44/0xae
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]  free_pages_prepare mm/page_alloc.c:1352 [inline]
 free_pcp_prepare+0x374/0x870 mm/page_alloc.c:1404  free_unref_page_prepare mm/page_alloc.c:3325 [inline]
 free_unref_page+0x19/0x690 mm/page_alloc.c:3404  slab_destroy mm/slab.c:1630 [inline]
 slabs_destroy+0x89/0xc0 mm/slab.c:1650
 cache_flusharray mm/slab.c:3410 [inline]
 ___cache_free+0x303/0x600 mm/slab.c:3472  qlink_free mm/kasan/quarantine.c:157 [inline]
 qlist_free_all+0x50/0x1a0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x180/0x200 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x97/0xb0 mm/kasan/common.c:446  kasan_slab_alloc include/linux/kasan.h:260 [inline]  slab_post_alloc_hook mm/slab.h:732 [inline]  slab_alloc_node mm/slab.c:3253 [inline]
 kmem_cache_alloc_node+0x2ea/0x590 mm/slab.c:3591
 __alloc_skb+0x215/0x340 net/core/skbuff.c:414  alloc_skb include/linux/skbuff.h:1158 [inline]
 alloc_skb_with_frags+0x93/0x620 net/core/skbuff.c:5956
 sock_alloc_send_pskb+0x793/0x920 net/core/sock.c:2586
 unix_dgram_sendmsg+0x414/0x1a10 net/unix/af_unix.c:1896  sock_sendmsg_nosec net/socket.c:705 [inline]
 sock_sendmsg+0xcf/0x120 net/socket.c:725
 __sys_sendto+0x21c/0x320 net/socket.c:2040  __do_sys_sendto net/socket.c:2052 [inline]  __se_sys_sendto net/socket.c:2048 [inline]
 __x64_sys_sendto+0xdd/0x1b0 net/socket.c:2048
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80

Memory state around the buggy address:
 ffff88802b933f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88802b934000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802b934080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88802b934100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802b934180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================

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