Patch "dccp: fix dccp_v4_err()/dccp_v6_err() again" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    dccp: fix dccp_v4_err()/dccp_v6_err() again

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dccp-fix-dccp_v4_err-dccp_v6_err-again.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit be1462fe96d264adf6c5d5da64dc58d490aab879
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Fri Sep 15 19:00:35 2023 +0000

    dccp: fix dccp_v4_err()/dccp_v6_err() again
    
    [ Upstream commit 6af289746a636f71f4c0535a9801774118486c7a ]
    
    dh->dccph_x is the 9th byte (offset 8) in "struct dccp_hdr",
    not in the "byte 7" as Jann claimed.
    
    We need to make sure the ICMP messages are big enough,
    using more standard ways (no more assumptions).
    
    syzbot reported:
    BUG: KMSAN: uninit-value in pskb_may_pull_reason include/linux/skbuff.h:2667 [inline]
    BUG: KMSAN: uninit-value in pskb_may_pull include/linux/skbuff.h:2681 [inline]
    BUG: KMSAN: uninit-value in dccp_v6_err+0x426/0x1aa0 net/dccp/ipv6.c:94
    pskb_may_pull_reason include/linux/skbuff.h:2667 [inline]
    pskb_may_pull include/linux/skbuff.h:2681 [inline]
    dccp_v6_err+0x426/0x1aa0 net/dccp/ipv6.c:94
    icmpv6_notify+0x4c7/0x880 net/ipv6/icmp.c:867
    icmpv6_rcv+0x19d5/0x30d0
    ip6_protocol_deliver_rcu+0xda6/0x2a60 net/ipv6/ip6_input.c:438
    ip6_input_finish net/ipv6/ip6_input.c:483 [inline]
    NF_HOOK include/linux/netfilter.h:304 [inline]
    ip6_input+0x15d/0x430 net/ipv6/ip6_input.c:492
    ip6_mc_input+0xa7e/0xc80 net/ipv6/ip6_input.c:586
    dst_input include/net/dst.h:468 [inline]
    ip6_rcv_finish+0x5db/0x870 net/ipv6/ip6_input.c:79
    NF_HOOK include/linux/netfilter.h:304 [inline]
    ipv6_rcv+0xda/0x390 net/ipv6/ip6_input.c:310
    __netif_receive_skb_one_core net/core/dev.c:5523 [inline]
    __netif_receive_skb+0x1a6/0x5a0 net/core/dev.c:5637
    netif_receive_skb_internal net/core/dev.c:5723 [inline]
    netif_receive_skb+0x58/0x660 net/core/dev.c:5782
    tun_rx_batched+0x83b/0x920
    tun_get_user+0x564c/0x6940 drivers/net/tun.c:2002
    tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
    call_write_iter include/linux/fs.h:1985 [inline]
    new_sync_write fs/read_write.c:491 [inline]
    vfs_write+0x8ef/0x15c0 fs/read_write.c:584
    ksys_write+0x20f/0x4c0 fs/read_write.c:637
    __do_sys_write fs/read_write.c:649 [inline]
    __se_sys_write fs/read_write.c:646 [inline]
    __x64_sys_write+0x93/0xd0 fs/read_write.c:646
    do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
    entry_SYSCALL_64_after_hwframe+0x63/0xcd
    
    Uninit was created at:
    slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
    slab_alloc_node mm/slub.c:3478 [inline]
    kmem_cache_alloc_node+0x577/0xa80 mm/slub.c:3523
    kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:559
    __alloc_skb+0x318/0x740 net/core/skbuff.c:650
    alloc_skb include/linux/skbuff.h:1286 [inline]
    alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6313
    sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2795
    tun_alloc_skb drivers/net/tun.c:1531 [inline]
    tun_get_user+0x23cf/0x6940 drivers/net/tun.c:1846
    tun_chr_write_iter+0x3af/0x5d0 drivers/net/tun.c:2048
    call_write_iter include/linux/fs.h:1985 [inline]
    new_sync_write fs/read_write.c:491 [inline]
    vfs_write+0x8ef/0x15c0 fs/read_write.c:584
    ksys_write+0x20f/0x4c0 fs/read_write.c:637
    __do_sys_write fs/read_write.c:649 [inline]
    __se_sys_write fs/read_write.c:646 [inline]
    __x64_sys_write+0x93/0xd0 fs/read_write.c:646
    do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
    entry_SYSCALL_64_after_hwframe+0x63/0xcd
    
    CPU: 0 PID: 4995 Comm: syz-executor153 Not tainted 6.6.0-rc1-syzkaller-00014-ga747acc0b752 #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
    
    Fixes: 977ad86c2a1b ("dccp: Fix out of bounds access in DCCP error handler")
    Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Cc: Jann Horn <jannh@xxxxxxxxxx>
    Reviewed-by: Jann Horn <jannh@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 8f5d3c0881118..247179d4c8865 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -255,13 +255,8 @@ static int dccp_v4_err(struct sk_buff *skb, u32 info)
 	int err;
 	struct net *net = dev_net(skb->dev);
 
-	/* For the first __dccp_basic_hdr_len() check, we only need dh->dccph_x,
-	 * which is in byte 7 of the dccp header.
-	 * Our caller (icmp_socket_deliver()) already pulled 8 bytes for us.
-	 *
-	 * Later on, we want to access the sequence number fields, which are
-	 * beyond 8 bytes, so we have to pskb_may_pull() ourselves.
-	 */
+	if (!pskb_may_pull(skb, offset + sizeof(*dh)))
+		return -EINVAL;
 	dh = (struct dccp_hdr *)(skb->data + offset);
 	if (!pskb_may_pull(skb, offset + __dccp_basic_hdr_len(dh)))
 		return -EINVAL;
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 2b09e2644b13f..6fb34eaf1237a 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -83,13 +83,8 @@ static int dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	__u64 seq;
 	struct net *net = dev_net(skb->dev);
 
-	/* For the first __dccp_basic_hdr_len() check, we only need dh->dccph_x,
-	 * which is in byte 7 of the dccp header.
-	 * Our caller (icmpv6_notify()) already pulled 8 bytes for us.
-	 *
-	 * Later on, we want to access the sequence number fields, which are
-	 * beyond 8 bytes, so we have to pskb_may_pull() ourselves.
-	 */
+	if (!pskb_may_pull(skb, offset + sizeof(*dh)))
+		return -EINVAL;
 	dh = (struct dccp_hdr *)(skb->data + offset);
 	if (!pskb_may_pull(skb, offset + __dccp_basic_hdr_len(dh)))
 		return -EINVAL;



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