Revision 9cc02ede696272c5271a401e4f27c262359bc2f6 authored by Duoming Zhou on 29 June 2022, 00:26:40 UTC, committed by Paolo Abeni on 30 June 2022, 09:07:30 UTC
There are UAF bugs in rose_heartbeat_expiry(), rose_timer_expiry()
and rose_idletimer_expiry(). The root cause is that del_timer()
could not stop the timer handler that is running and the refcount
of sock is not managed properly.
One of the UAF bugs is shown below:
(thread 1) | (thread 2)
| rose_bind
| rose_connect
| rose_start_heartbeat
rose_release | (wait a time)
case ROSE_STATE_0 |
rose_destroy_socket | rose_heartbeat_expiry
rose_stop_heartbeat |
sock_put(sk) | ...
sock_put(sk) // FREE |
| bh_lock_sock(sk) // USE
The sock is deallocated by sock_put() in rose_release() and
then used by bh_lock_sock() in rose_heartbeat_expiry().
Although rose_destroy_socket() calls rose_stop_heartbeat(),
it could not stop the timer that is running.
The KASAN report triggered by POC is shown below:
BUG: KASAN: use-after-free in _raw_spin_lock+0x5a/0x110
Write of size 4 at addr ffff88800ae59098 by task swapper/3/0
...
Call Trace:
<IRQ>
dump_stack_lvl+0xbf/0xee
print_address_description+0x7b/0x440
print_report+0x101/0x230
? irq_work_single+0xbb/0x140
? _raw_spin_lock+0x5a/0x110
kasan_report+0xed/0x120
? _raw_spin_lock+0x5a/0x110
kasan_check_range+0x2bd/0x2e0
_raw_spin_lock+0x5a/0x110
rose_heartbeat_expiry+0x39/0x370
? rose_start_heartbeat+0xb0/0xb0
call_timer_fn+0x2d/0x1c0
? rose_start_heartbeat+0xb0/0xb0
expire_timers+0x1f3/0x320
__run_timers+0x3ff/0x4d0
run_timer_softirq+0x41/0x80
__do_softirq+0x233/0x544
irq_exit_rcu+0x41/0xa0
sysvec_apic_timer_interrupt+0x8c/0xb0
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x1b/0x20
RIP: 0010:default_idle+0xb/0x10
RSP: 0018:ffffc9000012fea0 EFLAGS: 00000202
RAX: 000000000000bcae RBX: ffff888006660f00 RCX: 000000000000bcae
RDX: 0000000000000001 RSI: ffffffff843a11c0 RDI: ffffffff843a1180
RBP: dffffc0000000000 R08: dffffc0000000000 R09: ffffed100da36d46
R10: dfffe9100da36d47 R11: ffffffff83cf0950 R12: 0000000000000000
R13: 1ffff11000ccc1e0 R14: ffffffff8542af28 R15: dffffc0000000000
...
Allocated by task 146:
__kasan_kmalloc+0xc4/0xf0
sk_prot_alloc+0xdd/0x1a0
sk_alloc+0x2d/0x4e0
rose_create+0x7b/0x330
__sock_create+0x2dd/0x640
__sys_socket+0xc7/0x270
__x64_sys_socket+0x71/0x80
do_syscall_64+0x43/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0
Freed by task 152:
kasan_set_track+0x4c/0x70
kasan_set_free_info+0x1f/0x40
____kasan_slab_free+0x124/0x190
kfree+0xd3/0x270
__sk_destruct+0x314/0x460
rose_release+0x2fa/0x3b0
sock_close+0xcb/0x230
__fput+0x2d9/0x650
task_work_run+0xd6/0x160
exit_to_user_mode_loop+0xc7/0xd0
exit_to_user_mode_prepare+0x4e/0x80
syscall_exit_to_user_mode+0x20/0x40
do_syscall_64+0x4f/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0
This patch adds refcount of sock when we use functions
such as rose_start_heartbeat() and so on to start timer,
and decreases the refcount of sock when timer is finished
or deleted by functions such as rose_stop_heartbeat()
and so on. As a result, the UAF bugs could be mitigated.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Tested-by: Duoming Zhou <duoming@zju.edu.cn>
Link: https://lore.kernel.org/r/20220629002640.5693-1-duoming@zju.edu.cn
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
1 parent f8ebb3a
test_fpu.c
// SPDX-License-Identifier: GPL-2.0+
/*
* Test cases for using floating point operations inside a kernel module.
*
* This tests kernel_fpu_begin() and kernel_fpu_end() functions, especially
* when userland has modified the floating point control registers. The kernel
* state might depend on the state set by the userland thread that was active
* before a syscall.
*
* To facilitate the test, this module registers file
* /sys/kernel/debug/selftest_helpers/test_fpu, which when read causes a
* sequence of floating point operations. If the operations fail, either the
* read returns error status or the kernel crashes.
* If the operations succeed, the read returns "1\n".
*/
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/debugfs.h>
#include <asm/fpu/api.h>
static int test_fpu(void)
{
/*
* This sequence of operations tests that rounding mode is
* to nearest and that denormal numbers are supported.
* Volatile variables are used to avoid compiler optimizing
* the calculations away.
*/
volatile double a, b, c, d, e, f, g;
a = 4.0;
b = 1e-15;
c = 1e-310;
/* Sets precision flag */
d = a + b;
/* Result depends on rounding mode */
e = a + b / 2;
/* Denormal and very large values */
f = b / c;
/* Depends on denormal support */
g = a + c * f;
if (d > a && e > a && g > a)
return 0;
else
return -EINVAL;
}
static int test_fpu_get(void *data, u64 *val)
{
int status = -EINVAL;
kernel_fpu_begin();
status = test_fpu();
kernel_fpu_end();
*val = 1;
return status;
}
DEFINE_DEBUGFS_ATTRIBUTE(test_fpu_fops, test_fpu_get, NULL, "%lld\n");
static struct dentry *selftest_dir;
static int __init test_fpu_init(void)
{
selftest_dir = debugfs_create_dir("selftest_helpers", NULL);
if (!selftest_dir)
return -ENOMEM;
debugfs_create_file_unsafe("test_fpu", 0444, selftest_dir, NULL,
&test_fpu_fops);
return 0;
}
static void __exit test_fpu_exit(void)
{
debugfs_remove(selftest_dir);
}
module_init(test_fpu_init);
module_exit(test_fpu_exit);
MODULE_LICENSE("GPL");
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