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authorDae R. Jeong <threeearcat@gmail.com>2023-03-27 15:01:53 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-04-05 20:37:35 +0300
commitae13381da5ff0e8e084c0323c3cc0a945e43e9c7 (patch)
tree99e02897b0f4a4a4505a5c3f3005a02ec1793d41 /drivers/misc
parent48a6c7bced2a781c911497f073347bec5ab4d7a5 (diff)
downloadlinux-ae13381da5ff0e8e084c0323c3cc0a945e43e9c7.tar.xz
vmci_host: fix a race condition in vmci_host_poll() causing GPF
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: 8bf503991f87 ("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>
Diffstat (limited to 'drivers/misc')
-rw-r--r--drivers/misc/vmw_vmci/vmci_host.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/misc/vmw_vmci/vmci_host.c b/drivers/misc/vmw_vmci/vmci_host.c
index 857b9851402a..abe79f6fd2a7 100644
--- a/drivers/misc/vmw_vmci/vmci_host.c
+++ b/drivers/misc/vmw_vmci/vmci_host.c
@@ -165,10 +165,16 @@ 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,