From: Wang Hai wanghai38@huawei.com

[ Upstream commit 3bb2a01caa813d3a1845d378bbe4169ef280d394 ]

In kobject_get_path(), if kobj->name is changed between calls get_kobj_path_length() and fill_kobj_path() and the length becomes longer, then fill_kobj_path() will have an out-of-bounds bug.

The actual current problem occurs when the ixgbe probe.

In ixgbe_mii_bus_init(), if the length of netdev->dev.kobj.name length becomes longer, out-of-bounds will occur.

cpu0 cpu1 ixgbe_probe register_netdev(netdev) netdev_register_kobject device_add kobject_uevent // Sending ADD events systemd-udevd // rename netdev dev_change_name device_rename kobject_rename ixgbe_mii_bus_init | mdiobus_register | __mdiobus_register | device_register | device_add | kobject_uevent | kobject_get_path | len = get_kobj_path_length // old name | path = kzalloc(len, gfp_mask); | kobj->name = name; /* name length becomes * longer */ fill_kobj_path /* kobj path length is * longer than path, * resulting in out of * bounds when filling path */

This is the kasan report:

================================================================== BUG: KASAN: slab-out-of-bounds in fill_kobj_path+0x50/0xc0 Write of size 7 at addr ff1100090573d1fd by task kworker/28:1/673

Workqueue: events work_for_cpu_fn Call Trace: <TASK> dump_stack_lvl+0x34/0x48 print_address_description.constprop.0+0x86/0x1e7 print_report+0x36/0x4f kasan_report+0xad/0x130 kasan_check_range+0x35/0x1c0 memcpy+0x39/0x60 fill_kobj_path+0x50/0xc0 kobject_get_path+0x5a/0xc0 kobject_uevent_env+0x140/0x460 device_add+0x5c7/0x910 __mdiobus_register+0x14e/0x490 ixgbe_probe.cold+0x441/0x574 [ixgbe] local_pci_probe+0x78/0xc0 work_for_cpu_fn+0x26/0x40 process_one_work+0x3b6/0x6a0 worker_thread+0x368/0x520 kthread+0x165/0x1a0 ret_from_fork+0x1f/0x30

This reproducer triggers that bug:

while: do rmmod ixgbe sleep 0.5 modprobe ixgbe sleep 0.5

When calling fill_kobj_path() to fill path, if the name length of kobj becomes longer, return failure and retry. This fixes the problem.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Wang Hai wanghai38@huawei.com Link: https://lore.kernel.org/r/20221220012143.52141-1-wanghai38@huawei.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Oleksandr Tymoshenko ovt@google.com --- lib/kobject.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/kobject.c b/lib/kobject.c index cd3e1a98eff9..73047e847e91 100644 --- a/lib/kobject.c +++ b/lib/kobject.c @@ -144,7 +144,7 @@ static int get_kobj_path_length(struct kobject *kobj) return length; }

-static void fill_kobj_path(struct kobject *kobj, char *path, int length) +static int fill_kobj_path(struct kobject *kobj, char *path, int length) { struct kobject *parent;

@@ -153,12 +153,16 @@ static void fill_kobj_path(struct kobject *kobj, char *path, int length) int cur = strlen(kobject_name(parent)); /* back up enough to print this name with '/' */ length -= cur; + if (length <= 0) + return -EINVAL; memcpy(path + length, kobject_name(parent), cur); *(path + --length) = '/'; }

pr_debug("kobject: '%s' (%p): %s: path = '%s'\n", kobject_name(kobj), kobj, __func__, path); + + return 0; }

/** @@ -173,13 +177,17 @@ char *kobject_get_path(struct kobject *kobj, gfp_t gfp_mask) char *path; int len;

+retry: len = get_kobj_path_length(kobj); if (len == 0) return NULL; path = kzalloc(len, gfp_mask); if (!path) return NULL; - fill_kobj_path(kobj, path, len); + if (fill_kobj_path(kobj, path, len)) { + kfree(path); + goto retry; + }

return path; }