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Date: Sun, 8 Nov 2020 00:32:11 +0530 From: Anmol karn <anmol.karan123@...il.com> To: ralf@...ux-mips.org, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org> Cc: Saeed Mahameed <saeed@...nel.org>, Greg KH <gregkh@...uxfoundation.org>, netdev <netdev@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>, linux-hams@...r.kernel.org, linux-kernel-mentees@...ts.linuxfoundation.org, syzkaller-bugs@...glegroups.com, syzbot <syzbot+a1c743815982d9496393@...kaller.appspotmail.com> Subject: Re: [Linux-kernel-mentees] [PATCH v2] net: rose: Fix Null pointer dereference in rose_send_frame() Hello, Sorry for this wrong subject(It should be v3 instead of v2), please ignore this patch. I will send a new one with the corrected subject. Thanks, Anmol On Sun, Nov 8, 2020 at 12:27 AM Anmol Karn <anmol.karan123@...il.com> wrote: > > rose_send_frame() dereferences `neigh->dev` when called from > rose_transmit_clear_request(), and the first occurrence of the > `neigh` is in rose_loopback_timer() as `rose_loopback_neigh`, > and it is initialized in rose_add_loopback_neigh() as NULL. > i.e when `rose_loopback_neigh` used in rose_loopback_timer() > its `->dev` was still NULL and rose_loopback_timer() was calling > rose_rx_call_request() without checking for NULL. > > - net/rose/rose_link.c > This bug seems to get triggered in this line: > > rose_call = (ax25_address *)neigh->dev->dev_addr; > > Fix it by adding NULL checking for `rose_loopback_neigh->dev` > in rose_loopback_timer(). > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Reported-by: syzbot+a1c743815982d9496393@...kaller.appspotmail.com > Tested-by: syzbot+a1c743815982d9496393@...kaller.appspotmail.com > Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3 > Signed-off-by: Anmol Karn <anmol.karan123@...il.com> > --- > Changes in v3: > - Corrected checkpatch warnings and errors (Suggested-by: Saeed Mahameed <saeed@...nel.org>) > - Added "Fixes:" tag (Suggested-by: Saeed Mahameed <saeed@...nel.org>) > Changes in v2: > - Added NULL check in rose_loopback_timer() (Suggested-by: Greg KH <gregkh@...uxfoundation.org>) > > net/rose/rose_loopback.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/rose/rose_loopback.c b/net/rose/rose_loopback.c > index 7b094275ea8b..2c51756ed7bf 100644 > --- a/net/rose/rose_loopback.c > +++ b/net/rose/rose_loopback.c > @@ -96,7 +96,8 @@ static void rose_loopback_timer(struct timer_list *unused) > } > > if (frametype == ROSE_CALL_REQUEST) { > - if ((dev = rose_dev_get(dest)) != NULL) { > + dev = rose_dev_get(dest); > + if (rose_loopback_neigh->dev && dev) { > if (rose_rx_call_request(skb, dev, rose_loopback_neigh, lci_o) == 0) > kfree_skb(skb); > } else { > - > 2.29.2 >
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