linux-kernel - [PATCH] virt: acrn: fix a memory leak bug in acrn_dev

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Date:   Tue,  4 Jan 2022 11:45:01 +0800
From:   Zhou Qingyang <zhou1615@....edu>
To:     zhou1615@....edu
Cc:     kjlu@....edu, Fei Li <fei1.li@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Shuo Liu <shuo.a.liu@...el.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] virt: acrn: fix a memory leak bug in acrn_dev_ioctl()

In acrn_dev_ioctl(), vm_param is not released or passed out on the 
error path of "if ((vm_param->reserved0 | vm_param->reserved1) != 0)", 
which could lead to a memory leak.

Fix this bug by adding a kfree of vm_param on the error path.

This bug was found by a static analyzer.

Builds with CONFIG_ACRN_GUEST=y, CONFIG_ACRN_HSM=y show no new warnings, 
and our static analyzer no longer warns about this code.

Fixes: 9c5137aedd11 (“9c5137aedd11 virt: acrn: Introduce VM management interfaces”)
Signed-off-by: Zhou Qingyang <zhou1615@....edu>
---
The analysis employs differential checking to identify inconsistent
security operations (e.g., checks or kfrees) between two code paths
and confirms that the inconsistent operations are not recovered in 
the current function or the callers, so they constitute bugs. 

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

Changes in v2:
  -  Fix the same bug in ACRN_IOCTL_SET_VCPU_REGS.

 drivers/virt/acrn/hsm.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c
index 5419794fccf1..7a8f722f431c 100644
--- a/drivers/virt/acrn/hsm.c
+++ b/drivers/virt/acrn/hsm.c
@@ -136,9 +136,11 @@ static long acrn_dev_ioctl(struct file *filp, unsigned int cmd,
 		if (IS_ERR(vm_param))
 			return PTR_ERR(vm_param);
 
-		if ((vm_param->reserved0 | vm_param->reserved1) != 0)
-			return -EINVAL;
-
+		if ((vm_param->reserved0 | vm_param->reserved1) != 0) {
+			ret = -EINVAL;
+			kfree(vm_param);
+			break;
+		}
 		vm = acrn_vm_create(vm, vm_param);
 		if (!vm) {
 			ret = -EINVAL;
@@ -182,21 +184,29 @@ static long acrn_dev_ioctl(struct file *filp, unsigned int cmd,
 			return PTR_ERR(cpu_regs);
 
 		for (i = 0; i < ARRAY_SIZE(cpu_regs->reserved); i++)
-			if (cpu_regs->reserved[i])
+			if (cpu_regs->reserved[i]) {
+				kfree(cpu_regs);
 				return -EINVAL;
+			}
 
 		for (i = 0; i < ARRAY_SIZE(cpu_regs->vcpu_regs.reserved_32); i++)
-			if (cpu_regs->vcpu_regs.reserved_32[i])
+			if (cpu_regs->vcpu_regs.reserved_32[i]) {
+				kfree(cpu_regs);
 				return -EINVAL;
+			}
 
 		for (i = 0; i < ARRAY_SIZE(cpu_regs->vcpu_regs.reserved_64); i++)
-			if (cpu_regs->vcpu_regs.reserved_64[i])
+			if (cpu_regs->vcpu_regs.reserved_64[i]) {
+				kfree(cpu_regs);
 				return -EINVAL;
+			}
 
 		for (i = 0; i < ARRAY_SIZE(cpu_regs->vcpu_regs.gdt.reserved); i++)
 			if (cpu_regs->vcpu_regs.gdt.reserved[i] |
-			    cpu_regs->vcpu_regs.idt.reserved[i])
+			    cpu_regs->vcpu_regs.idt.reserved[i]) {
+				kfree(cpu_regs);
 				return -EINVAL;
+			}
 
 		ret = hcall_set_vcpu_regs(vm->vmid, virt_to_phys(cpu_regs));
 		if (ret < 0)
-- 
2.25.1