From: Dae R. Jeong <threeearcat@xxxxxxxxx>
[ 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@xxxxxxxxx>
Fixes: 8bf503991f87 ("VMCI: host side driver implementation.")
Signed-off-by: Dae R. Jeong <threeearcat@xxxxxxxxx>
Link: https://lore.kernel.org/r/ZCGFsdBAU4cYww5l@dragonet
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/misc/vmw_vmci/vmci_host.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/misc/vmw_vmci/vmci_host.c b/drivers/misc/vmw_vmci/vmci_host.c
index 83e0c95d20a47..5acbf384ffa64 100644
--- a/drivers/misc/vmw_vmci/vmci_host.c
+++ b/drivers/misc/vmw_vmci/vmci_host.c
@@ -169,10 +169,16 @@ 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,
--
2.39.2
