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([2601:647:6700:3390::c8d1]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2365d8a1972sm5580895ad.55.2025.06.12.21.24.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Jun 2025 21:24:13 -0700 (PDT) From: Kuniyuki Iwashima To: syzbot+1d3c235276f62963e93a@syzkaller.appspotmail.com Cc: 3chas3@gmail.com, kuni1840@gmail.com, kuniyu@google.com, linux-atm-general@lists.sourceforge.net, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [atm?] KMSAN: uninit-value in atmtcp_c_send Date: Thu, 12 Jun 2025 21:24:05 -0700 Message-ID: <20250613042412.328342-1-kuni1840@gmail.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <684b9f72.050a0220.be214.0299.GAE@google.com> References: <684b9f72.050a0220.be214.0299.GAE@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: syzbot Date: Thu, 12 Jun 2025 20:48:02 -0700 > Hello, > > syzbot has tested the proposed patch and the reproducer did not trigger any issue: > > Reported-by: syzbot+1d3c235276f62963e93a@syzkaller.appspotmail.com > Tested-by: syzbot+1d3c235276f62963e93a@syzkaller.appspotmail.com > > Tested on: > > commit: 27605c8c Merge tag 'net-6.16-rc2' of git://git.kernel... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=16d17682580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=42d51b7b9f9e61d > dashboard link: https://syzkaller.appspot.com/bug?extid=1d3c235276f62963e93a > compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6 > patch: https://syzkaller.appspot.com/x/patch.diff?x=129e7682580000 > > Note: testing is done by a robot and is best-effort only. I noticed the original code didn't call dev_kfree_skb() and leaked sk_buff_head. Also, most of the ATM drivers don't call atm_return() to revert the memory accounting by atm_account_tx() in vcc_sendmsg(), but that's another bug... #syz test diff --git a/drivers/atm/atmtcp.c b/drivers/atm/atmtcp.c index d4aa0f353b6c..5ce3c6c066e1 100644 --- a/drivers/atm/atmtcp.c +++ b/drivers/atm/atmtcp.c @@ -288,7 +288,11 @@ static int atmtcp_c_send(struct atm_vcc *vcc,struct sk_buff *skb) struct sk_buff *new_skb; int result = 0; - if (!skb->len) return 0; + if (skb->len < sizeof(struct atmtcp_hdr)) { + dev_kfree_skb(skb); + return -EINVAL; + } + dev = vcc->dev_data; hdr = (struct atmtcp_hdr *) skb->data; if (hdr->length == ATMTCP_HDR_MAGIC) {