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Eric W. Biederman authored
Alexandar Potapenko while testing the kernel with KMSAN and syzkaller discovered that in some configurations sctp would leak 4 bytes of kernel stack. Working with his reproducer I discovered that those 4 bytes that are leaked is the scope id of an ipv6 address returned by recvmsg. With a little code inspection and a shrewd guess I discovered that sctp_inet6_skb_msgname only initializes the scope_id field for link local ipv6 addresses to the interface index the link local address pertains to instead of initializing the scope_id field for all ipv6 addresses. That is almost reasonable as scope_id's are meaniningful only for link local addresses. Set the scope_id in all other cases to 0 which is not a valid interface index to make it clear there is nothing useful in the scope_id field. There should be no danger of breaking userspace as the stack leak guaranteed that previously meaningless random data was being returned. Fixes: 372f525b ("SCTP: Resync with LKSCTP tree.") History-tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.gitReported-by:
Alexander Potapenko <glider@google.com> Tested-by:
Alexander Potapenko <glider@google.com> Signed-off-by:
"Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by:
David S. Miller <davem@davemloft.net>
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