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llc: fix data loss when reading from a socket in llc_ui_recvmsg() 

commit 239af1970b upstream.

For SOCK_STREAM sockets, if user buffer size (len) is less
than skb size (skb->len), the remaining data from skb
will be lost after calling kfree_skb().

To fix this, move the statement for partial reading
above skb deletion.

Found by InfoTeCS on behalf of Linux Verification Center (linuxtesting.org)

Fixes: 30a584d944 ("[LLX]: SOCK_DGRAM interface fixes")
Cc: stable@vger.kernel.org
Signed-off-by: Ilia Gavrilov <Ilia.Gavrilov@infotecs.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 4cfe30f681a3df21b77f3d4c668069d6d0cf9840)
This commit is contained in:
Ilia Gavrilov 2025-05-15 12:20:15 +00:00 committed by Wentao Guan
parent e2c5827264
commit 99ee2d9cf5
1 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
net/llc/af_llc.c
View File

@ -888,15 +888,15 @@ static int llc_ui_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
if (sk->sk_type != SOCK_STREAM)
goto copy_uaddr;
/* Partial read */
if (used + offset < skb_len)
continue;
if (!(flags & MSG_PEEK)) {
skb_unlink(skb, &sk->sk_receive_queue);
kfree_skb(skb);
*seq = 0;
}
/* Partial read */
if (used + offset < skb_len)
continue;
} while (len > 0);
out: