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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <000000000000b2585a05fdeb8379@google.com>
References: <000000000000b2585a05fdeb8379@google.com>
To:     syzbot <syzbot+6efc50cc1f8d718d6cb7@syzkaller.appspotmail.com>
Cc:     dhowells@redhat.com, davem@davemloft.net,
        herbert@gondor.apana.org.au, kuba@kernel.org,
        linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [crypto?] KASAN: slab-out-of-bounds Read in extract_iter_to_sg
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Content-ID: <89570.1686830867.1@warthog.procyon.org.uk>
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Date:   Thu, 15 Jun 2023 13:07:47 +0100
Message-ID: <89571.1686830867@warthog.procyon.org.uk>
Precedence: bulk

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.g=
it main

diff --git a/fs/splice.c b/fs/splice.c
index 67ddaac1f5c5..17d692449e83 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -886,7 +886,6 @@ ssize_t splice_to_socket(struct pipe_inode_info *pipe,=
 struct file *out,
 			}
 =

 			seg =3D min_t(size_t, remain, buf->len);
-			seg =3D min_t(size_t, seg, PAGE_SIZE);
 =

 			ret =3D pipe_buf_confirm(pipe, buf);
 			if (unlikely(ret)) {
@@ -897,10 +896,9 @@ ssize_t splice_to_socket(struct pipe_inode_info *pipe=
, struct file *out,
 =

 			bvec_set_page(&bvec[bc++], buf->page, seg, buf->offset);
 			remain -=3D seg;
-			if (seg >=3D buf->len)
-				tail++;
-			if (bc >=3D ARRAY_SIZE(bvec))
+			if (remain =3D=3D 0 || bc >=3D ARRAY_SIZE(bvec))
 				break;
+			tail++;
 		}
 =

 		if (!bc)
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 457598dfa128..6e70839257f7 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1041,7 +1041,8 @@ static int __ip_append_data(struct sock *sk,
 	} else if ((flags & MSG_SPLICE_PAGES) && length) {
 		if (inet->hdrincl)
 			return -EPERM;
-		if (rt->dst.dev->features & NETIF_F_SG)
+		if (rt->dst.dev->features & NETIF_F_SG &&
+		    getfrag =3D=3D ip_generic_getfrag)
 			/* We need an empty buffer to attach stuff to */
 			paged =3D true;
 		else
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index c06ff7519f19..1e8c90e97608 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1593,7 +1593,8 @@ static int __ip6_append_data(struct sock *sk,
 	} else if ((flags & MSG_SPLICE_PAGES) && length) {
 		if (inet_sk(sk)->hdrincl)
 			return -EPERM;
-		if (rt->dst.dev->features & NETIF_F_SG)
+		if (rt->dst.dev->features & NETIF_F_SG &&
+		    getfrag =3D=3D ip_generic_getfrag)
 			/* We need an empty buffer to attach stuff to */
 			paged =3D true;
 		else