Messages in this thread | | | Date | Mon, 19 Dec 2022 15:54:40 +0100 | From | Greg KH <> | Subject | Re: [PATCH] kobject: Fix slab-out-of-bounds in fill_kobj_path() |
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On Mon, Dec 19, 2022 at 10:41:03PM +0800, Wang Hai wrote: > 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. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Wang Hai <wanghai38@huawei.com> > --- > lib/kobject.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-)
Nice find, and a much better description than was reported here: https://lore.kernel.org/all/20221216031320.2634-1-alice.chao@mediatek.com/
Alice, does this patch resolve your problem as well?
> > diff --git a/lib/kobject.c b/lib/kobject.c > index a0b2dbfcfa23..d129f437b200 100644 > --- a/lib/kobject.c > +++ b/lib/kobject.c > @@ -112,7 +112,7 @@ static int get_kobj_path_length(struct kobject *kobj) > return length; > } > > -static void fill_kobj_path(struct kobject *kobj, char *path, int length) > +static bool fill_kobj_path(struct kobject *kobj, char *path, int length)
Just return an int and an error value, bool isn't a normal return value, right?
> { > struct kobject *parent; > > @@ -121,12 +121,16 @@ 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 false;
Return -EINVAL or something?
What if length ends up 0 here, is that going to be ok?
> 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 true;
return 0;
> } > > /** > @@ -140,14 +144,20 @@ char *kobject_get_path(struct kobject *kobj, gfp_t gfp_mask) > { > char *path; > int len; > + bool ret;
No need for this variable
> > +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); > + ret = fill_kobj_path(kobj, path, len); > + if (!ret) {
Make this one line:
if (fill_kobj_path(kobj, path, len)) {
But, you now have a loop, what guarantees that you can get out of it?
thanks,
greg k-h
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