| From bippy-1.2.0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@kernel.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2025-37843: PCI: pciehp: Avoid unnecessary device replacement check |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| PCI: pciehp: Avoid unnecessary device replacement check |
| |
| Hot-removal of nested PCI hotplug ports suffers from a long-standing race |
| condition which can lead to a deadlock: A parent hotplug port acquires |
| pci_lock_rescan_remove(), then waits for pciehp to unbind from a child |
| hotplug port. Meanwhile that child hotplug port tries to acquire |
| pci_lock_rescan_remove() as well in order to remove its own children. |
| |
| The deadlock only occurs if the parent acquires pci_lock_rescan_remove() |
| first, not if the child happens to acquire it first. |
| |
| Several workarounds to avoid the issue have been proposed and discarded |
| over the years, e.g.: |
| |
| https://lore.kernel.org/r/4c882e25194ba8282b78fe963fec8faae7cf23eb.1529173804.git.lukas@wunner.de/ |
| |
| A proper fix is being worked on, but needs more time as it is nontrivial |
| and necessarily intrusive. |
| |
| Recent commit 9d573d19547b ("PCI: pciehp: Detect device replacement during |
| system sleep") provokes more frequent occurrence of the deadlock when |
| removing more than one Thunderbolt device during system sleep. The commit |
| sought to detect device replacement, but also triggered on device removal. |
| Differentiating reliably between replacement and removal is impossible |
| because pci_get_dsn() returns 0 both if the device was removed, as well as |
| if it was replaced with one lacking a Device Serial Number. |
| |
| Avoid the more frequent occurrence of the deadlock by checking whether the |
| hotplug port itself was hot-removed. If so, there's no sense in checking |
| whether its child device was replaced. |
| |
| This works because the ->resume_noirq() callback is invoked in top-down |
| order for the entire hierarchy: A parent hotplug port detecting device |
| replacement (or removal) marks all children as removed using |
| pci_dev_set_disconnected() and a child hotplug port can then reliably |
| detect being removed. |
| |
| The Linux kernel CVE team has assigned CVE-2025-37843 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.11 with commit 9d573d19547b3fae0c1d4e5fce52bdad3fda3664 and fixed in 6.12.24 with commit e4a1d7defbc2d806540720a5adebe24ec3488683 |
| Issue introduced in 6.11 with commit 9d573d19547b3fae0c1d4e5fce52bdad3fda3664 and fixed in 6.13.12 with commit 0d0bbd01f7c0ac7d1be9f85aaf2cd0baec34655f |
| Issue introduced in 6.11 with commit 9d573d19547b3fae0c1d4e5fce52bdad3fda3664 and fixed in 6.14.3 with commit 7535d10a2c61baeff493300070cf04d9ddda216b |
| Issue introduced in 6.11 with commit 9d573d19547b3fae0c1d4e5fce52bdad3fda3664 and fixed in 6.15 with commit e3260237aaadc9799107ccb940c6688195c4518d |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2025-37843 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| drivers/pci/hotplug/pciehp_core.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/e4a1d7defbc2d806540720a5adebe24ec3488683 |
| https://git.kernel.org/stable/c/0d0bbd01f7c0ac7d1be9f85aaf2cd0baec34655f |
| https://git.kernel.org/stable/c/7535d10a2c61baeff493300070cf04d9ddda216b |
| https://git.kernel.org/stable/c/e3260237aaadc9799107ccb940c6688195c4518d |
