[PATCH] virt: acrn: fix memory leak in acrn_dev_ioctl()

[PATCH] virt: acrn: fix memory leak in acrn_dev_ioctl()

[Zhou Qingyang]

In acrn_dev_ioctl(), cpu_regs is not released or passed out on several 
error paths which could lead to memory leak bug.

Fix this bug by adding kfree of cpu_regs on error paths.

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: 2ad2aaee1bc9 ("virt: acrn: Introduce an ioctl to set vCPU registers state")
Signed-off-by: Zhou Qingyang <zhou1615@umn.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.

 drivers/virt/acrn/hsm.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c
index 5419794fccf1..1eb0a17aadde 100644
--- a/drivers/virt/acrn/hsm.c
+++ b/drivers/virt/acrn/hsm.c
@@ -182,21 +182,29 @@ 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])
-				return -EINVAL;
+			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])
-				return -EINVAL;
+			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])
-				return -EINVAL;
+			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])
-				return -EINVAL;
+			    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

Re: [PATCH] virt: acrn: fix memory leak in acrn_dev_ioctl()

[Greg Kroah-Hartman]

On Tue, Jan 04, 2022 at 04:53:21PM +0800, Zhou Qingyang wrote:
> In acrn_dev_ioctl(), cpu_regs is not released or passed out on several 
> error paths which could lead to memory leak bug.
> 
> Fix this bug by adding kfree of cpu_regs on error paths.
> 
> 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: 2ad2aaee1bc9 ("virt: acrn: Introduce an ioctl to set vCPU registers state")
> Signed-off-by: Zhou Qingyang <zhou1615@umn.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.

Then why have all of those researchers put their reviewed-by on this
change?

Note that your university is still in many kernel maintainer's
ignore-list (myself included, I dug this up as I saw Fei's response.)
Please work with your administration and the process that is currently
happening in order to give you all the needed training so you will not
keep causing these types of basic errors that keep your patches from
being accepted.

*plonk*

greg k-h