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vmci_host: fix a race condition in vmci_host_poll() causing GPF

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[ Upstream commit ae13381da5ff0e8e084c0323c3cc0a945e43e9c7 ]

During fuzzing, a general protection fault is observed in
vmci_host_poll().

general protection fault, probably for non-canonical address 0xdffffc0000000019: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x00000000000000c8-0x00000000000000cf]
RIP: 0010:__lock_acquire+0xf3/0x5e00 kernel/locking/lockdep.c:4926
<- omitting registers ->
Call Trace:
 <TASK>
 lock_acquire+0x1a4/0x4a0 kernel/locking/lockdep.c:5672
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xb3/0x100 kernel/locking/spinlock.c:162
 add_wait_queue+0x3d/0x260 kernel/sched/wait.c:22
 poll_wait include/linux/poll.h:49 [inline]
 vmci_host_poll+0xf8/0x2b0 drivers/misc/vmw_vmci/vmci_host.c:174
 vfs_poll include/linux/poll.h:88 [inline]
 do_pollfd fs/select.c:873 [inline]
 do_poll fs/select.c:921 [inline]
 do_sys_poll+0xc7c/0x1aa0 fs/select.c:1015
 __do_sys_ppoll fs/select.c:1121 [inline]
 __se_sys_ppoll+0x2cc/0x330 fs/select.c:1101
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4e/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Example thread interleaving that causes the general protection fault
is as follows:

CPU1 (vmci_host_poll)               CPU2 (vmci_host_do_init_context)
-----                               -----
// Read uninitialized context
context = vmci_host_dev->context;
                                    // Initialize context
                                    vmci_host_dev->context = vmci_ctx_create();
                                    vmci_host_dev->ct_type = VMCIOBJ_CONTEXT;

if (vmci_host_dev->ct_type == VMCIOBJ_CONTEXT) {
    // Dereferencing the wrong pointer
    poll_wait(..., &context->host_context);
}

In this scenario, vmci_host_poll() reads vmci_host_dev->context first,
and then reads vmci_host_dev->ct_type to check that
vmci_host_dev->context is initialized. However, since these two reads
are not atomically executed, there is a chance of a race condition as
described above.

To fix this race condition, read vmci_host_dev->context after checking
the value of vmci_host_dev->ct_type so that vmci_host_poll() always
reads an initialized context.

Reported-by: Dae R. Jeong <threeearcat@gmail.com>
Fixes: 8bf503991f ("VMCI: host side driver implementation.")
Signed-off-by: Dae R. Jeong <threeearcat@gmail.com>
Link: https://lore.kernel.org/r/ZCGFsdBAU4cYww5l@dragonet
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Dae R. Jeong 2023-03-27 21:01:53 +09:00 committed by Greg Kroah-Hartman
parent 170e223240
commit ca0f4ad2b7
1 changed files with 7 additions and 1 deletions
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8
drivers/misc/vmw_vmci/vmci_host.c
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@ -160,10 +160,16 @@ static int vmci_host_close(struct inode *inode, struct file *filp)
static __poll_t vmci_host_poll(struct file *filp, poll_table *wait)
{
struct vmci_host_dev *vmci_host_dev = filp->private_data;
struct vmci_ctx *context = vmci_host_dev->context;
struct vmci_ctx *context;
__poll_t mask = 0;
if (vmci_host_dev->ct_type == VMCIOBJ_CONTEXT) {
/*
* Read context only if ct_type == VMCIOBJ_CONTEXT to make
* sure that context is initialized
*/
context = vmci_host_dev->context;
/* Check for VMCI calls to this VM context. */
if (wait)
poll_wait(filp, &context->host_context.wait_queue,