If xhci_mem_init() fails, it calls into xhci_mem_cleanup() to mop
up the damage. If it fails early enough, before xhci->interrupters
is allocated but after xhci->max_interrupters has been set, which
happens in most (all?) cases, things get uglier, as xhci_mem_cleanup()
unconditionally derefences xhci->interrupters. With prejudice.

Gate the interrupt freeing loop with a check on xhci->interrupters
being non-NULL.

Found while debugging a DMA allocation issue that led the XHCI driver
on this exact path.

Fixes: c99b38c41234 ("xhci: add support to allocate several interrupters")
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: Wesley Cheng <quic_wcheng@quicinc.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 drivers/usb/host/xhci-mem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index d7654f475daf..937ce5fd5809 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -1872,7 +1872,7 @@ void xhci_mem_cleanup(struct xhci_hcd *xhci)
 
 	cancel_delayed_work_sync(&xhci->cmd_timer);
 
-	for (i = 0; i < xhci->max_interrupters; i++) {
+	for (i = 0; xhci->interrupters && i < xhci->max_interrupters; i++) {
 		if (xhci->interrupters[i]) {
 			xhci_remove_interrupter(xhci, xhci->interrupters[i]);
 			xhci_free_interrupter(xhci, xhci->interrupters[i]);
-- 
2.39.2

On 31.7.2024 23.59, Marc Zyngier wrote:
> If xhci_mem_init() fails, it calls into xhci_mem_cleanup() to mop
> up the damage. If it fails early enough, before xhci->interrupters
> is allocated but after xhci->max_interrupters has been set, which
> happens in most (all?) cases, things get uglier, as xhci_mem_cleanup()
> unconditionally derefences xhci->interrupters. With prejudice.
> 
> Gate the interrupt freeing loop with a check on xhci->interrupters
> being non-NULL.
> 
> Found while debugging a DMA allocation issue that led the XHCI driver
> on this exact path.
> 
> Fixes: c99b38c41234 ("xhci: add support to allocate several interrupters")
> Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
> Cc: Wesley Cheng <quic_wcheng@quicinc.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---

Thanks, Adding to queue

-Mathias