| Message ID | 20210602192640.13597-1-paskripkin@gmail.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | net: kcm: fix memory leak in kcm_sendmsg | expand |
On Thu, 3 Jun 2021 15:32:03 -0700 Cong Wang <xiyou.wangcong@gmail.com> wrote: > On Wed, Jun 2, 2021 at 12:29 PM Pavel Skripkin <paskripkin@gmail.com> > wrote: > > > > Syzbot reported memory leak in kcm_sendmsg()[1]. > > The problem was in non-freed frag_list in case of error. > > > > In the while loop: > > > > if (head == skb) > > skb_shinfo(head)->frag_list = tskb; > > else > > skb->next = tskb; > > > > frag_list filled with skbs, but nothing was freeing them. > > What do you mean by "nothing was freeing them"? > > I am sure kfree_skb() will free those in frag_list: > > 654 static void skb_release_data(struct sk_buff *skb) > 655 { > 656 struct skb_shared_info *shinfo = skb_shinfo(skb); > 657 int i; > ... > 669 if (shinfo->frag_list) > 670 kfree_skb_list(shinfo->frag_list); > > Indeed. I didn't know about that. Im sorry. > > > > backtrace: > > [<0000000094c02615>] __alloc_skb+0x5e/0x250 net/core/skbuff.c:198 > > [<00000000e5386cbd>] alloc_skb include/linux/skbuff.h:1083 > > [inline] [<00000000e5386cbd>] kcm_sendmsg+0x3b6/0xa50 > > net/kcm/kcmsock.c:967 [1] [<00000000f1613a8a>] sock_sendmsg_nosec > > net/socket.c:652 [inline] [<00000000f1613a8a>] > > sock_sendmsg+0x4c/0x60 net/socket.c:672 > > > > Reported-and-tested-by: > > syzbot+b039f5699bd82e1fb011@syzkaller.appspotmail.com Fixes: > > ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Cc: > > stable@vger.kernel.org Signed-off-by: Pavel Skripkin > > <paskripkin@gmail.com> --- > > net/kcm/kcmsock.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c > > index 6201965bd822..1c572c8daced 100644 > > --- a/net/kcm/kcmsock.c > > +++ b/net/kcm/kcmsock.c > > @@ -1066,6 +1066,11 @@ static int kcm_sendmsg(struct socket *sock, > > struct msghdr *msg, size_t len) goto partial_message; > > } > > > > + if (skb_has_frag_list(head)) { > > + kfree_skb_list(skb_shinfo(head)->frag_list); > > + skb_shinfo(head)->frag_list = NULL; > > + } > > + > > if (head != kcm->seq_skb) > > kfree_skb(head); > > This exact kfree_skb() should free those in frag_list. If the above > if condition does not meet for some reason, then fix that condition? > > Thanks. I will debug this today later. I think, this commit should be reverted, because it's broken. Or I can send next patch on top of this. What do you think of that, David? With regards, Pavel Skripkin
diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c index 6201965bd822..1c572c8daced 100644 --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -1066,6 +1066,11 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) goto partial_message; } + if (skb_has_frag_list(head)) { + kfree_skb_list(skb_shinfo(head)->frag_list); + skb_shinfo(head)->frag_list = NULL; + } + if (head != kcm->seq_skb) kfree_skb(head);
Syzbot reported memory leak in kcm_sendmsg()[1]. The problem was in non-freed frag_list in case of error. In the while loop: if (head == skb) skb_shinfo(head)->frag_list = tskb; else skb->next = tskb; frag_list filled with skbs, but nothing was freeing them. backtrace: [<0000000094c02615>] __alloc_skb+0x5e/0x250 net/core/skbuff.c:198 [<00000000e5386cbd>] alloc_skb include/linux/skbuff.h:1083 [inline] [<00000000e5386cbd>] kcm_sendmsg+0x3b6/0xa50 net/kcm/kcmsock.c:967 [1] [<00000000f1613a8a>] sock_sendmsg_nosec net/socket.c:652 [inline] [<00000000f1613a8a>] sock_sendmsg+0x4c/0x60 net/socket.c:672 Reported-and-tested-by: syzbot+b039f5699bd82e1fb011@syzkaller.appspotmail.com Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Cc: stable@vger.kernel.org Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> --- net/kcm/kcmsock.c | 5 +++++ 1 file changed, 5 insertions(+)