From d293ca716e7d5dffdaecaf6b9b2f857a33dc3d3a Mon Sep 17 00:00:00 2001 From: Lee Jones Date: Tue, 21 Apr 2026 13:45:26 +0100 Subject: [PATCH] tipc: fix double-free in tipc_buf_append() tipc_msg_validate() can potentially reallocate the skb it is validating, freeing the old one. In tipc_buf_append(), it was being called with a pointer to a local variable which was a copy of the caller's skb pointer. If the skb was reallocated and validation subsequently failed, the error handling path would free the original skb pointer, which had already been freed, leading to double-free. Fix this by checking if head now points to a newly allocated reassembled skb. If it does, reassign *headbuf for later freeing operations. Fixes: d618d09a68e4 ("tipc: enforce valid ratio between skb truesize and contents") Suggested-by: Tung Nguyen Signed-off-by: Lee Jones Reviewed-by: Tung Nguyen Signed-off-by: Jakub Kicinski --- net/tipc/msg.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/net/tipc/msg.c b/net/tipc/msg.c index 76284fc538eb..b0bba0feef56 100644 --- a/net/tipc/msg.c +++ b/net/tipc/msg.c @@ -177,8 +177,20 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf) if (fragid == LAST_FRAGMENT) { TIPC_SKB_CB(head)->validated = 0; - if (unlikely(!tipc_msg_validate(&head))) + + /* If the reassembled skb has been freed in + * tipc_msg_validate() because of an invalid truesize, + * then head will point to a newly allocated reassembled + * skb, while *headbuf points to freed reassembled skb. + * In such cases, correct *headbuf for freeing the newly + * allocated reassembled skb later. + */ + if (unlikely(!tipc_msg_validate(&head))) { + if (head != *headbuf) + *headbuf = head; goto err; + } + *buf = head; TIPC_SKB_CB(head)->tail = NULL; *headbuf = NULL;