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Message-ID: <20240905204249.27077-1-kuniyu@amazon.com> Date: Thu, 5 Sep 2024 13:42:49 -0700 From: Kuniyuki Iwashima <kuniyu@...zon.com> To: <rao.shoaib@...cle.com> CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>, <kuniyu@...zon.com>, <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>, <pabeni@...hat.com>, <syzbot+8811381d455e3e9ec788@...kaller.appspotmail.com>, <syzkaller-bugs@...glegroups.com> Subject: Re: [syzbot] [net?] KASAN: slab-use-after-free Read in unix_stream_read_actor (2) From: Shoaib Rao <rao.shoaib@...cle.com> Date: Thu, 5 Sep 2024 13:37:06 -0700 > On 9/5/2024 1:15 PM, Shoaib Rao wrote: > > > > On 9/5/2024 12:46 PM, Kuniyuki Iwashima wrote: > >> From: Shoaib Rao <rao.shoaib@...cle.com> > >> Date: Thu, 5 Sep 2024 00:35:35 -0700 > >>> Hi All, > >>> > >>> I am not able to reproduce the issue. I have run the C program at least > >>> 100 times in a loop. In the I do get an EFAULT, not sure if that is > >>> intentional or not but no panic. Should I be doing something > >>> differently? The kernel version I am using is > >>> v6.11-rc6-70-gc763c4339688. Later I can try with the exact version. > >> The -EFAULT is the bug meaning that we were trying to read an > >> consumed skb. > >> > >> But the first bug is in recvfrom() that shouldn't be able to read OOB > >> skb > >> without MSG_OOB, which doesn't clear unix_sk(sk)->oob_skb, and later > >> something bad happens. > >> > >> socketpair(AF_UNIX, SOCK_STREAM, 0, [3, 4]) = 0 > >> sendmsg(4, {msg_name=NULL, msg_namelen=0, > >> msg_iov=[{iov_base="\333", iov_len=1}], msg_iovlen=1, > >> msg_controllen=0, msg_flags=0}, MSG_OOB|MSG_DONTWAIT) = 1 > >> recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=NULL, > >> msg_iovlen=0, msg_controllen=0, msg_flags=MSG_OOB}, > >> MSG_OOB|MSG_WAITFORONE) = 1 > >> sendmsg(4, {msg_name=NULL, msg_namelen=0, > >> msg_iov=[{iov_base="\21", iov_len=1}], msg_iovlen=1, > >> msg_controllen=0, msg_flags=0}, MSG_OOB|MSG_NOSIGNAL|MSG_MORE) = 1 > >>> recvfrom(3, "\21", 125, MSG_DONTROUTE|MSG_TRUNC|MSG_DONTWAIT, NULL, > >>> NULL) = 1 > >> recvmsg(3, {msg_namelen=0}, MSG_OOB|MSG_ERRQUEUE) = -1 EFAULT (Bad > >> address) > >> > >> I posted a fix officially: > >> https://urldefense.com/v3/__https://lore.kernel.org/netdev/20240905193240.17565-5-kuniyu@amazon.com/__;!!ACWV5N9M2RV99hQ!IJeFvLdaXIRN2ABsMFVaKOEjI3oZb2kUr6ld6ZRJCPAVum4vuyyYwUP6_5ZH9mGZiJDn6vrbxBAOqYI$ > >> > > > > Thanks that is great. Isn't EFAULT, normally indicative of an issue > > with the user provided address of the buffer, not the kernel buffer. > > > > Shoaib > > > Can you provide the full test case that you used to reproduce the issue. I used the syzbot's repro, but you can check a new test case added in my patch.
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