| Message ID | 20240708115615.134770-1-dmantipov@yandex.ru (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | f2aeb7306a898e1cbd03963d376f4b6656ca2b55 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net,v2] ppp: reject claimed-as-LCP but actually malformed packets | expand |
+ Guillaume, Jakub On Mon, Jul 08, 2024 at 02:56:15PM +0300, Dmitry Antipov wrote: > Since 'ppp_async_encode()' assumes valid LCP packets (with code > from 1 to 7 inclusive), add 'ppp_check_packet()' to ensure that > LCP packet has an actual body beyond PPP_LCP header bytes, and > reject claimed-as-LCP but actually malformed data otherwise. > > Reported-by: syzbot+ec0723ba9605678b14bf@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf > Fixes: 44073187990d ("ppp: ensure minimum packet size in ppp_write()") Sorry for not noticing this earlier. I think that the cited commit is not where this problem was introduced. What that commit does is to introduce a length check. And what this patch does is to add another, more specific length check. But the problem fixed by this patch existed before the cited commit. I expect that, like the cited commit, this patch: Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> > --- > v2: style, comments, and metadata adjustments suggested by Simon Horman Thanks, other than the Fixes tag, this looks good to me. Reviewed-by: Simon Horman <horms@kernel.org> ...
On Tue, 2024-07-09 at 09:30 +0100, Simon Horman wrote: > + Guillaume, Jakub > > On Mon, Jul 08, 2024 at 02:56:15PM +0300, Dmitry Antipov wrote: > > Since 'ppp_async_encode()' assumes valid LCP packets (with code > > from 1 to 7 inclusive), add 'ppp_check_packet()' to ensure that > > LCP packet has an actual body beyond PPP_LCP header bytes, and > > reject claimed-as-LCP but actually malformed data otherwise. > > > > Reported-by: syzbot+ec0723ba9605678b14bf@syzkaller.appspotmail.com > > Closes: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf > > Fixes: 44073187990d ("ppp: ensure minimum packet size in ppp_write()") > > Sorry for not noticing this earlier. > > I think that the cited commit is not where this problem was introduced. > What that commit does is to introduce a length check. > And what this patch does is to add another, more specific length check. > But the problem fixed by this patch existed before the cited commit. > > I expect that, like the cited commit, this patch: > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") No need to resend, I'll update the tag while applying the patch. Thanks! Paolo
Hello: This patch was applied to netdev/net.git (main) by Paolo Abeni <pabeni@redhat.com>: On Mon, 8 Jul 2024 14:56:15 +0300 you wrote: > Since 'ppp_async_encode()' assumes valid LCP packets (with code > from 1 to 7 inclusive), add 'ppp_check_packet()' to ensure that > LCP packet has an actual body beyond PPP_LCP header bytes, and > reject claimed-as-LCP but actually malformed data otherwise. > > Reported-by: syzbot+ec0723ba9605678b14bf@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf > Fixes: 44073187990d ("ppp: ensure minimum packet size in ppp_write()") > Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> > > [...] Here is the summary with links: - [net,v2] ppp: reject claimed-as-LCP but actually malformed packets https://git.kernel.org/netdev/net/c/f2aeb7306a89 You are awesome, thank you!
diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c index 0a65b6d690fe..eb9acfcaeb09 100644 --- a/drivers/net/ppp/ppp_generic.c +++ b/drivers/net/ppp/ppp_generic.c @@ -70,6 +70,7 @@ #define MPHDRLEN_SSN 4 /* ditto with short sequence numbers */ #define PPP_PROTO_LEN 2 +#define PPP_LCP_HDRLEN 4 /* * An instance of /dev/ppp can be associated with either a ppp @@ -493,6 +494,15 @@ static ssize_t ppp_read(struct file *file, char __user *buf, return ret; } +static bool ppp_check_packet(struct sk_buff *skb, size_t count) +{ + /* LCP packets must include LCP header which 4 bytes long: + * 1-byte code, 1-byte identifier, and 2-byte length. + */ + return get_unaligned_be16(skb->data) != PPP_LCP || + count >= PPP_PROTO_LEN + PPP_LCP_HDRLEN; +} + static ssize_t ppp_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { @@ -515,6 +525,11 @@ static ssize_t ppp_write(struct file *file, const char __user *buf, kfree_skb(skb); goto out; } + ret = -EINVAL; + if (unlikely(!ppp_check_packet(skb, count))) { + kfree_skb(skb); + goto out; + } switch (pf->kind) { case INTERFACE:
Since 'ppp_async_encode()' assumes valid LCP packets (with code from 1 to 7 inclusive), add 'ppp_check_packet()' to ensure that LCP packet has an actual body beyond PPP_LCP header bytes, and reject claimed-as-LCP but actually malformed data otherwise. Reported-by: syzbot+ec0723ba9605678b14bf@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf Fixes: 44073187990d ("ppp: ensure minimum packet size in ppp_write()") Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> --- v2: style, comments, and metadata adjustments suggested by Simon Horman --- drivers/net/ppp/ppp_generic.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)