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Message-ID: <2025050118-CVE-2025-37786-cbe7@gregkh> Date: Thu, 1 May 2025 15:07:33 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-cve-announce@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...nel.org> Subject: CVE-2025-37786: net: dsa: free routing table on probe failure From: Greg Kroah-Hartman <gregkh@...nel.org> 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-rc3 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
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