Re: [Linux-kernel-mentees] [PATCH v2] net: rose: Fix Null pointer dereference in rose_send_frame()
From: Anmol karn <hidden>
Date: 2020-11-07 19:02:27
Also in:
linux-hams, linux-kernel-mentees, lkml
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 [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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@syzkaller.appspotmail.com Tested-by: syzbot+a1c743815982d9496393@syzkaller.appspotmail.com Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3 Signed-off-by: Anmol Karn <redacted> --- Changes in v3: - Corrected checkpatch warnings and errors (Suggested-by: Saeed Mahameed [off-list ref]) - Added "Fixes:" tag (Suggested-by: Saeed Mahameed [off-list ref]) Changes in v2: - Added NULL check in rose_loopback_timer() (Suggested-by: Greg KH [off-list ref]) 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