xhci_alloc_command() allocates a command structure and, when the
second argument is true, also allocates a completion structure.
Currently, the error handling path in xhci_disable_slot() only frees
the command structure using kfree(), causing the completion structure
to leak.

Use xhci_free_command() instead of kfree(). xhci_free_command() correctly
frees both the command structure and the associated completion structure.
Since the command structure is allocated with zero-initialization,
command->in_ctx is NULL and will not be erroneously freed by
xhci_free_command().

This bug was found using an experimental static analysis tool we are
developing. The tool is based on the LLVM framework and is specifically
designed to detect memory management issues. It is currently under
active development and not yet publicly available, but we plan to
open-source it after our research is published.

The analysis was performed on Linux kernel v6.13-rc1.

We performed build testing on x86_64 with allyesconfig using GCC=11.4.0.
Since triggering these error paths in xhci_disable_slot() requires specific
hardware conditions or abnormal state, we were unable to construct a test
case to reliably trigger these specific error paths at runtime.

Fixes: 7faac1953ed1 ("xhci: avoid race between disable slot command and host runtime suspend")
CC: stable@vger.kernel.org
Signed-off-by: Zilin Guan <zilin@seu.edu.cn>
---
Changes in v2:
- Add detailed information required by researcher guidelines.
- Clarify the safety of using xhci_free_command() in this context.
- Correct the Fixes tag to point to the commit that introduced this issue.

 drivers/usb/host/xhci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 02c9bfe21ae2..f0beed054954 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4137,7 +4137,7 @@ int xhci_disable_slot(struct xhci_hcd *xhci, u32 slot_id)
 	if (state == 0xffffffff || (xhci->xhc_state & XHCI_STATE_DYING) ||
 			(xhci->xhc_state & XHCI_STATE_HALTED)) {
 		spin_unlock_irqrestore(&xhci->lock, flags);
-		kfree(command);
+		xhci_free_command(xhci, command);
 		return -ENODEV;
 	}
 
@@ -4145,7 +4145,7 @@ int xhci_disable_slot(struct xhci_hcd *xhci, u32 slot_id)
 				slot_id);
 	if (ret) {
 		spin_unlock_irqrestore(&xhci->lock, flags);
-		kfree(command);
+		xhci_free_command(xhci, command);
 		return ret;
 	}
 	xhci_ring_cmd_db(xhci);
-- 
2.34.1

On Thu, Jan 08, 2026 at 02:11:08PM +0000, Zilin Guan wrote:
> xhci_alloc_command() allocates a command structure and, when the
> second argument is true, also allocates a completion structure.
> Currently, the error handling path in xhci_disable_slot() only frees
> the command structure using kfree(), causing the completion structure
> to leak.
> 
> Use xhci_free_command() instead of kfree(). xhci_free_command() correctly
> frees both the command structure and the associated completion structure.
> Since the command structure is allocated with zero-initialization,
> command->in_ctx is NULL and will not be erroneously freed by
> xhci_free_command().
> 
> This bug was found using an experimental static analysis tool we are
> developing. The tool is based on the LLVM framework and is specifically
> designed to detect memory management issues. It is currently under
> active development and not yet publicly available, but we plan to
> open-source it after our research is published.
> 
> The analysis was performed on Linux kernel v6.13-rc1.

That is a very old kernel version, from December 2024, please redo this
to verify it is relevent to todays tree.

thanks,

greg k-h

On Thu, Jan 08, 2026 at 04:28:42PM +0100, Greg KH wrote:
> On Thu, Jan 08, 2026 at 02:11:08PM +0000, Zilin Guan wrote:
> > xhci_alloc_command() allocates a command structure and, when the
> > second argument is true, also allocates a completion structure.
> > Currently, the error handling path in xhci_disable_slot() only frees
> > the command structure using kfree(), causing the completion structure
> > to leak.
> > 
> > Use xhci_free_command() instead of kfree(). xhci_free_command() correctly
> > frees both the command structure and the associated completion structure.
> > Since the command structure is allocated with zero-initialization,
> > command->in_ctx is NULL and will not be erroneously freed by
> > xhci_free_command().
> > 
> > This bug was found using an experimental static analysis tool we are
> > developing. The tool is based on the LLVM framework and is specifically
> > designed to detect memory management issues. It is currently under
> > active development and not yet publicly available, but we plan to
> > open-source it after our research is published.
> > 
> > The analysis was performed on Linux kernel v6.13-rc1.
> 
> That is a very old kernel version, from December 2024, please redo this
> to verify it is relevent to todays tree.
> 
> thanks,
> 
> greg k-h

Sorry for the confusion caused by our description. While the static 
analysis was indeed performed on v6.13-rc1, we have manually verified 
that the bug still exists in the latest mainline kernel before submitting
the patch.

I will clarify this distinction in the v3 patch and update the version 
information.

Thanks,
Zilin Guan