This is a note to let you know that I've just added the patch titled misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge to the 5.13-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: misc-alcor_pci-fix-null-ptr-deref-when-there-is-no-p.patch and it can be found in the queue-5.13 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit cedf7c0d2d7aed66ad5ef4fcb271361441847443 Author: Tong Zhang <ztong0001@xxxxxxxxx> Date: Thu May 13 00:07:33 2021 -0400 misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge [ Upstream commit 3ce3e45cc333da707d4d6eb433574b990bcc26f5 ] There is an issue with the ASPM(optional) capability checking function. A device might be attached to root complex directly, in this case, bus->self(bridge) will be NULL, thus priv->parent_pdev is NULL. Since alcor_pci_init_check_aspm(priv->parent_pdev) checks the PCI link's ASPM capability and populate parent_cap_off, which will be used later by alcor_pci_aspm_ctrl() to dynamically turn on/off device, what we can do here is to avoid checking the capability if we are on the root complex. This will make pdev_cap_off 0 and alcor_pci_aspm_ctrl() will simply return when bring called, effectively disable ASPM for the device. [ 1.246492] BUG: kernel NULL pointer dereference, address: 00000000000000c0 [ 1.248731] RIP: 0010:pci_read_config_byte+0x5/0x40 [ 1.253998] Call Trace: [ 1.254131] ? alcor_pci_find_cap_offset.isra.0+0x3a/0x100 [alcor_pci] [ 1.254476] alcor_pci_probe+0x169/0x2d5 [alcor_pci] Co-developed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Tong Zhang <ztong0001@xxxxxxxxx> Link: https://lore.kernel.org/r/20210513040732.1310159-1-ztong0001@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/misc/cardreader/alcor_pci.c b/drivers/misc/cardreader/alcor_pci.c index cd402c89189e..0a62307f7ffb 100644 --- a/drivers/misc/cardreader/alcor_pci.c +++ b/drivers/misc/cardreader/alcor_pci.c @@ -139,7 +139,13 @@ static void alcor_pci_init_check_aspm(struct alcor_pci_priv *priv) u32 val32; priv->pdev_cap_off = alcor_pci_find_cap_offset(priv, priv->pdev); - priv->parent_cap_off = alcor_pci_find_cap_offset(priv, + /* + * A device might be attached to root complex directly and + * priv->parent_pdev will be NULL. In this case we don't check its + * capability and disable ASPM completely. + */ + if (!priv->parent_pdev) + priv->parent_cap_off = alcor_pci_find_cap_offset(priv, priv->parent_pdev); if ((priv->pdev_cap_off == 0) || (priv->parent_cap_off == 0)) {