net/tls: fix kernel panic when alloc_page failed

JIRA: https://issues.redhat.com/browse/RHEL-115640

commit 491deb9
Author: Pengtao He <hept.hept.hept@gmail.com>
Date:   Wed May 14 21:20:13 2025 +0800

    net/tls: fix kernel panic when alloc_page failed

    We cannot set frag_list to NULL pointer when alloc_page failed.
    It will be used in tls_strp_check_queue_ok when the next time
    tls_strp_read_sock is called.

    This is because we don't reset full_len in tls_strp_flush_anchor_copy()
    so the recv path will try to continue handling the partial record
    on the next call but we dettached the rcvq from the frag list.
    Alternative fix would be to reset full_len.

    Unable to handle kernel NULL pointer dereference
    at virtual address 0000000000000028
     Call trace:
     tls_strp_check_rcv+0x128/0x27c
     tls_strp_data_ready+0x34/0x44
     tls_data_ready+0x3c/0x1f0
     tcp_data_ready+0x9c/0xe4
     tcp_data_queue+0xf6c/0x12d0
     tcp_rcv_established+0x52c/0x798

    Fixes: 84c61fe ("tls: rx: do not use the standard strparser")
    Signed-off-by: Pengtao He <hept.hept.hept@gmail.com>
    Link: https://patch.msgid.link/20250514132013.17274-1-hept.hept.hept@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: Sabrina Dubroca <sdubroca@redhat.com>

Author: Sabrina Dubroca

net/tls/tls_strp.c

@@ -395,7 +395,6 @@ static int tls_strp_read_copy(struct tls_strparser *strp, bool qshort)
 		return 0;
 
 	shinfo = skb_shinfo(strp->anchor);
-	shinfo->frag_list = NULL;
 
 	/* If we don't know the length go max plus page for cipher overhead */
 	need_spc = strp->stm.full_len ?: TLS_MAX_PAYLOAD_SIZE + PAGE_SIZE;
@@ -411,6 +410,8 @@ static int tls_strp_read_copy(struct tls_strparser *strp, bool qshort)
 				   page, 0, 0);
 	}
 
+	shinfo->frag_list = NULL;
+
 	strp->copy_mode = 1;
 	strp->stm.offset = 0;