| 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-2025-37786: net: dsa: free routing table on probe failure |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| net: dsa: free routing table on probe failure |
| |
| If complete = true in dsa_tree_setup(), it means that we are the last |
| switch of the tree which is successfully probing, and we should be |
| setting up all switches from our probe path. |
| |
| After "complete" becomes true, dsa_tree_setup_cpu_ports() or any |
| subsequent function may fail. If that happens, the entire tree setup is |
| in limbo: the first N-1 switches have successfully finished probing |
| (doing nothing but having allocated persistent memory in the tree's |
| dst->ports, and maybe dst->rtable), and switch N failed to probe, ending |
| the tree setup process before anything is tangible from the user's PoV. |
| |
| If switch N fails to probe, its memory (ports) will be freed and removed |
| from dst->ports. However, the dst->rtable elements pointing to its ports, |
| as created by dsa_link_touch(), will remain there, and will lead to |
| use-after-free if dereferenced. |
| |
| If dsa_tree_setup_switches() returns -EPROBE_DEFER, which is entirely |
| possible because that is where ds->ops->setup() is, we get a kasan |
| report like this: |
| |
| ================================================================== |
| BUG: KASAN: slab-use-after-free in mv88e6xxx_setup_upstream_port+0x240/0x568 |
| Read of size 8 at addr ffff000004f56020 by task kworker/u8:3/42 |
| |
| Call trace: |
| __asan_report_load8_noabort+0x20/0x30 |
| mv88e6xxx_setup_upstream_port+0x240/0x568 |
| mv88e6xxx_setup+0xebc/0x1eb0 |
| dsa_register_switch+0x1af4/0x2ae0 |
| mv88e6xxx_register_switch+0x1b8/0x2a8 |
| mv88e6xxx_probe+0xc4c/0xf60 |
| mdio_probe+0x78/0xb8 |
| really_probe+0x2b8/0x5a8 |
| __driver_probe_device+0x164/0x298 |
| driver_probe_device+0x78/0x258 |
| __device_attach_driver+0x274/0x350 |
| |
| Allocated by task 42: |
| __kasan_kmalloc+0x84/0xa0 |
| __kmalloc_cache_noprof+0x298/0x490 |
| dsa_switch_touch_ports+0x174/0x3d8 |
| dsa_register_switch+0x800/0x2ae0 |
| mv88e6xxx_register_switch+0x1b8/0x2a8 |
| mv88e6xxx_probe+0xc4c/0xf60 |
| mdio_probe+0x78/0xb8 |
| really_probe+0x2b8/0x5a8 |
| __driver_probe_device+0x164/0x298 |
| driver_probe_device+0x78/0x258 |
| __device_attach_driver+0x274/0x350 |
| |
| Freed by task 42: |
| __kasan_slab_free+0x48/0x68 |
| kfree+0x138/0x418 |
| dsa_register_switch+0x2694/0x2ae0 |
| mv88e6xxx_register_switch+0x1b8/0x2a8 |
| mv88e6xxx_probe+0xc4c/0xf60 |
| mdio_probe+0x78/0xb8 |
| really_probe+0x2b8/0x5a8 |
| __driver_probe_device+0x164/0x298 |
| driver_probe_device+0x78/0x258 |
| __device_attach_driver+0x274/0x350 |
| |
| The simplest way to fix the bug is to delete the routing table in its |
| entirety. dsa_tree_setup_routing_table() has no problem in regenerating |
| it even if we deleted links between ports other than those of switch N, |
| because dsa_link_touch() first checks whether the port pair already |
| exists in dst->rtable, allocating if not. |
| |
| The deletion of the routing table in its entirety already exists in |
| dsa_tree_teardown(), so refactor that into a function that can also be |
| called from the tree setup error path. |
| |
| In my analysis of the commit to blame, it is the one which added |
| dsa_link elements to dst->rtable. Prior to that, each switch had its own |
| ds->rtable which is freed when the switch fails to probe. But the tree |
| is potentially persistent memory. |
| |
| The Linux kernel CVE team has assigned CVE-2025-37786 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.5 with commit c5f51765a1f60b701840544faf3ca63204b8dc3c and fixed in 6.6.88 with commit fb12b460ec46c9efad98de6d9ba349691db51dc7 |
| Issue introduced in 5.5 with commit c5f51765a1f60b701840544faf3ca63204b8dc3c and fixed in 6.12.25 with commit 5c8066fbdb9653c6e9a224bdcd8f9c91a484f0de |
| Issue introduced in 5.5 with commit c5f51765a1f60b701840544faf3ca63204b8dc3c and fixed in 6.14.4 with commit a038f5f15af455dfe35bc68549e02b950978700a |
| Issue introduced in 5.5 with commit c5f51765a1f60b701840544faf3ca63204b8dc3c and fixed in 6.15 with commit 8bf108d7161ffc6880ad13a0cc109de3cf631727 |
| |
| 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-2025-37786 |
| 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: |
| net/dsa/dsa.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/fb12b460ec46c9efad98de6d9ba349691db51dc7 |
| https://git.kernel.org/stable/c/5c8066fbdb9653c6e9a224bdcd8f9c91a484f0de |
| https://git.kernel.org/stable/c/a038f5f15af455dfe35bc68549e02b950978700a |
| https://git.kernel.org/stable/c/8bf108d7161ffc6880ad13a0cc109de3cf631727 |
