Message ID | 20210812091501.22648-1-paskripkin@gmail.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | block: nbd: add sanity check for first_minor | expand |
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
On 8/12/21 12:15 PM, Pavel Skripkin wrote: > Syzbot hit WARNING in internal_create_group(). The problem was in > too big disk->first_minor. > > disk->first_minor is initialized by value, which comes from userspace > and there wasn't any sanity checks about value correctness. It can cause > duplicate creation of sysfs files/links, because disk->first_minor will > be passed to MKDEV() which causes truncation to byte. Since maximum > minor value is 0xff, let's check if first_minor is correct minor number. > > NOTE: the root case of the reported warning was in wrong error handling > in register_disk(), but we can avoid passing knowingly wrong values to > sysfs API, because sysfs error messages can confuse users. For example: > user passed 1048576 as index, but sysfs complains about duplicate > creation of /dev/block/43:0. It's not obvious how 1048576 becomes 0. > Log and reproducer for above example can be found on syzkaller bug > report page. > > Link: https://syzkaller.appspot.com/bug?id=03c2ae9146416edf811958d5fd7acfab75b143d1 > Fixes: b0d9111a2d53 ("nbd: use an idr to keep track of nbd devices") > Reported-by: syzbot+9937dc42271cd87d4b98@syzkaller.appspotmail.com > Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> > --- > drivers/block/nbd.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > index c38317979f74..600e9bab5d43 100644 > --- a/drivers/block/nbd.c > +++ b/drivers/block/nbd.c > @@ -1725,7 +1725,17 @@ static int nbd_dev_add(int index) > refcount_set(&nbd->refs, 1); > INIT_LIST_HEAD(&nbd->list); > disk->major = NBD_MAJOR; > + > + /* Too big first_minor can cause duplicate creation of > + * sysfs files/links, since first_minor will be truncated to > + * byte in __device_add_disk(). > + */ > disk->first_minor = index << part_shift; > + if (disk->first_minor > 0xff) { > + err = -EINVAL; > + goto out_free_idr; > + } > + > disk->minors = 1 << part_shift; > disk->fops = &nbd_fops; > disk->private_data = nbd; > Fun thing: I got a reply to this email from nsd-public@police.gov.hk, which is Hong Kong Police office email. Does anyone know what is going on? :) It's a bit scary... With regards, Pavel Skripkin
On Thu, Aug 12, 2021 at 12:42:38PM +0300, Pavel Skripkin wrote: > > Fun thing: I got a reply to this email from > nsd-public@police.gov.hk, which is Hong Kong Police office email. Does > anyone know what is going on? :) It's a bit scary... You are not alone. Apparently, someone subscribed that address to the nbd@other.debian.org list and it is auto-responding to every message it receives; hopefully, a list administrator (I am not one) will be willing to forcefully unsubscribe that address.
On Thu, Aug 12, 2021 at 10:35:25AM -0500, Eric Blake wrote: > On Thu, Aug 12, 2021 at 12:42:38PM +0300, Pavel Skripkin wrote: > > > > Fun thing: I got a reply to this email from > > nsd-public@police.gov.hk, which is Hong Kong Police office email. Does > > anyone know what is going on? :) It's a bit scary... > > You are not alone. Apparently, someone subscribed that address to the > nbd@other.debian.org list and it is auto-responding to every message > it receives; hopefully, a list administrator (I am not one) will be > willing to forcefully unsubscribe that address. FWIW, this has now happened, so you should no longer see such autoreplies.
On Mon, Aug 16, 2021 at 05:26:23PM +0200, Wouter Verhelst wrote: > On Thu, Aug 12, 2021 at 10:35:25AM -0500, Eric Blake wrote: > > On Thu, Aug 12, 2021 at 12:42:38PM +0300, Pavel Skripkin wrote: > > > > > > Fun thing: I got a reply to this email from > > > nsd-public@police.gov.hk, which is Hong Kong Police office email. Does > > > anyone know what is going on? :) It's a bit scary... > > > > You are not alone. Apparently, someone subscribed that address to the > > nbd@other.debian.org list and it is auto-responding to every message > > it receives; hopefully, a list administrator (I am not one) will be > > willing to forcefully unsubscribe that address. > > FWIW, this has now happened, so you should no longer see such autoreplies. ... except I just received another one myself. I've taken it up with the list admins again. I won't update the whole Cc list of this anymore, but rest assured I'll stay on this until it's been taken care of.
On 8/12/21 3:15 AM, Pavel Skripkin wrote: > Syzbot hit WARNING in internal_create_group(). The problem was in > too big disk->first_minor. > > disk->first_minor is initialized by value, which comes from userspace > and there wasn't any sanity checks about value correctness. It can cause > duplicate creation of sysfs files/links, because disk->first_minor will > be passed to MKDEV() which causes truncation to byte. Since maximum > minor value is 0xff, let's check if first_minor is correct minor number. > > NOTE: the root case of the reported warning was in wrong error handling > in register_disk(), but we can avoid passing knowingly wrong values to > sysfs API, because sysfs error messages can confuse users. For example: > user passed 1048576 as index, but sysfs complains about duplicate > creation of /dev/block/43:0. It's not obvious how 1048576 becomes 0. > Log and reproducer for above example can be found on syzkaller bug > report page. Applied, thanks.
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index c38317979f74..600e9bab5d43 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1725,7 +1725,17 @@ static int nbd_dev_add(int index) refcount_set(&nbd->refs, 1); INIT_LIST_HEAD(&nbd->list); disk->major = NBD_MAJOR; + + /* Too big first_minor can cause duplicate creation of + * sysfs files/links, since first_minor will be truncated to + * byte in __device_add_disk(). + */ disk->first_minor = index << part_shift; + if (disk->first_minor > 0xff) { + err = -EINVAL; + goto out_free_idr; + } + disk->minors = 1 << part_shift; disk->fops = &nbd_fops; disk->private_data = nbd;
Syzbot hit WARNING in internal_create_group(). The problem was in too big disk->first_minor. disk->first_minor is initialized by value, which comes from userspace and there wasn't any sanity checks about value correctness. It can cause duplicate creation of sysfs files/links, because disk->first_minor will be passed to MKDEV() which causes truncation to byte. Since maximum minor value is 0xff, let's check if first_minor is correct minor number. NOTE: the root case of the reported warning was in wrong error handling in register_disk(), but we can avoid passing knowingly wrong values to sysfs API, because sysfs error messages can confuse users. For example: user passed 1048576 as index, but sysfs complains about duplicate creation of /dev/block/43:0. It's not obvious how 1048576 becomes 0. Log and reproducer for above example can be found on syzkaller bug report page. Link: https://syzkaller.appspot.com/bug?id=03c2ae9146416edf811958d5fd7acfab75b143d1 Fixes: b0d9111a2d53 ("nbd: use an idr to keep track of nbd devices") Reported-by: syzbot+9937dc42271cd87d4b98@syzkaller.appspotmail.com Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- drivers/block/nbd.c | 10 ++++++++++ 1 file changed, 10 insertions(+)