[PATCH 5.9 199/255] uio: Fix use-after-free in uio_unregister_device()

Greg Kroah-Hartman
2020-11-17T13:39:59Z

From: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>

commit 092561f06702dd4fdd7fb74dd3a838f1818529b7 upstream.

Commit 8fd0e2a6df26 ("uio: free uio id after uio file node is freed")
triggered KASAN use-after-free failure at deletion of TCM-user
backstores [1].

In uio_unregister_device(), struct uio_device *idev is passed to
uio_free_minor() to refer idev->minor. However, before uio_free_minor()
call, idev is already freed by uio_device_release() during call to
device_unregister().

To avoid reference to idev->minor after idev free, keep idev->minor
value in a local variable. Also modify uio_free_minor() argument to
receive the value.

[1]
BUG: KASAN: use-after-free in uio_unregister_device+0x166/0x190
Read of size 4 at addr ffff888105196508 by task targetcli/49158

CPU: 3 PID: 49158 Comm: targetcli Not tainted 5.10.0-rc1 #1
Hardware name: Supermicro Super Server/X10SRL-F, BIOS 2.0 12/17/2015
Call Trace:
dump_stack+0xae/0xe5
? uio_unregister_device+0x166/0x190
print_address_description.constprop.0+0x1c/0x210
? uio_unregister_device+0x166/0x190
? uio_unregister_device+0x166/0x190
kasan_report.cold+0x37/0x7c
? kobject_put+0x80/0x410
? uio_unregister_device+0x166/0x190
uio_unregister_device+0x166/0x190
tcmu_destroy_device+0x1c4/0x280 [target_core_user]
? tcmu_release+0x90/0x90 [target_core_user]
? __mutex_unlock_slowpath+0xd6/0x5d0
target_free_device+0xf3/0x2e0 [target_core_mod]
config_item_cleanup+0xea/0x210
configfs_rmdir+0x651/0x860
? detach_groups.isra.0+0x380/0x380
vfs_rmdir.part.0+0xec/0x3a0
? __lookup_hash+0x20/0x150
do_rmdir+0x252/0x320
? do_file_open_root+0x420/0x420
? strncpy_from_user+0xbc/0x2f0
? getname_flags.part.0+0x8e/0x450
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f9e2bfc91fb
Code: 73 01 c3 48 8b 0d 9d ec 0c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa b8 54 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 6d ec 0c 00 f7 d8 64 89 01 48
RSP: 002b:00007ffdd2baafe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 00007f9e2beb44a0 RCX: 00007f9e2bfc91fb
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00007f9e1c20be90
RBP: 00007ffdd2bab000 R08: 0000000000000000 R09: 00007f9e2bdf2440
R10: 00007ffdd2baaf37 R11: 0000000000000246 R12: 00000000ffffff9c
R13: 000055f9abb7e390 R14: 000055f9abcf9558 R15: 00007f9e2be7a780

Allocated by task 34735:
kasan_save_stack+0x1b/0x40
__kasan_kmalloc.constprop.0+0xc2/0xd0
__uio_register_device+0xeb/0xd40
tcmu_configure_device+0x5a0/0xbc0 [target_core_user]
target_configure_device+0x12f/0x760 [target_core_mod]
target_dev_enable_store+0x32/0x50 [target_core_mod]
configfs_write_file+0x2bb/0x450
vfs_write+0x1ce/0x610
ksys_write+0xe9/0x1b0
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 49158:
kasan_save_stack+0x1b/0x40
kasan_set_track+0x1c/0x30
kasan_set_free_info+0x1b/0x30
__kasan_slab_free+0x110/0x150
slab_free_freelist_hook+0x5a/0x170
kfree+0xc6/0x560
device_release+0x9b/0x210
kobject_put+0x13e/0x410
uio_unregister_device+0xf9/0x190
tcmu_destroy_device+0x1c4/0x280 [target_core_user]
target_free_device+0xf3/0x2e0 [target_core_mod]
config_item_cleanup+0xea/0x210
configfs_rmdir+0x651/0x860
vfs_rmdir.part.0+0xec/0x3a0
do_rmdir+0x252/0x320
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff888105196000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 1288 bytes inside of
2048-byte region [ffff888105196000, ffff888105196800)
The buggy address belongs to the page:
page:0000000098e6ca81 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x105190
head:0000000098e6ca81 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x17ffffc0010200(slab|head)
raw: 0017ffffc0010200 dead000000000100 dead000000000122 ffff888100043040
raw: 0000000000000000 0000000000080008 00000001ffffffff ffff88810eb55c01
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff88810eb55c01

Memory state around the buggy address:
ffff888105196400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888105196480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888105196500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888105196580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888105196600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

Fixes: 8fd0e2a6df26 ("uio: free uio id after uio file node is freed")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://lore.kernel.org/r/20201102122819.2346270-1-shinichiro.kawasaki@wdc.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/uio/uio.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -413,10 +413,10 @@ static int uio_get_minor(struct uio_devi
return retval;
}

-static void uio_free_minor(struct uio_device *idev)
+static void uio_free_minor(unsigned long minor)
{
mutex_lock(&minor_lock);
- idr_remove(&uio_idr, idev->minor);
+ idr_remove(&uio_idr, minor);
mutex_unlock(&minor_lock);
}

@@ -990,7 +990,7 @@ err_request_irq:
err_uio_dev_add_attributes:
device_del(&idev->dev);
err_device_create:
- uio_free_minor(idev);
+ uio_free_minor(idev->minor);
put_device(&idev->dev);
return ret;
}
@@ -1042,11 +1042,13 @@ EXPORT_SYMBOL_GPL(__devm_uio_register_de
void uio_unregister_device(struct uio_info *info)
{
struct uio_device *idev;
+ unsigned long minor;

if (!info || !info->uio_dev)
return;

idev = info->uio_dev;
+ minor = idev->minor;

mutex_lock(&idev->info_lock);
uio_dev_del_attributes(idev);
@@ -1062,7 +1064,7 @@ void uio_unregister_device(struct uio_in

device_unregister(&idev->dev);

- uio_free_minor(idev);
+ uio_free_minor(minor);

return;
}