On 3/31/22 10:28, Paolo Abeni wrote:
On Tue, 2022-03-29 at 18:12 +0200, Niels Dossche wrote:Currently, n->keepalive_intv is written to while n is locked by a read lock instead of a write lock. This seems to me to break the atomicity against other readers. Change this to a write lock instead to solve the issue. Note: I am currently working on a static analyser to detect missing locks using type-based static analysis as my master's thesis in order to obtain my master's degree. If you would like to have more details, please let me know. This was a reported case. I manually verified the report by looking at the code, so that I do not send wrong information or patches. After concluding that this seems to be a true positive, I created this patch. I have both compile-tested this patch and runtime-tested this patch on x86_64. The effect on a running system could be a potential race condition in exceptional cases. This issue was found on Linux v5.17. Fixes: f5d6c3e5a359 ("tipc: fix node keep alive interval calculation") Signed-off-by: Niels Dossche <dossche.ni...@gmail.com> --- net/tipc/node.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/tipc/node.c b/net/tipc/node.c index 6ef95ce565bd..da867ddb93f5 100644 --- a/net/tipc/node.c +++ b/net/tipc/node.c @@ -806,9 +806,9 @@ static void tipc_node_timeout(struct timer_list *t) /* Initial node interval to value larger (10 seconds), then it will be * recalculated with link lowest tolerance */ - tipc_node_read_lock(n); + tipc_node_write_lock(n);I agree with Hoang, this should be safe even without write lock, as tipc_node_timeout() is the only function modifying keepalive_intv, and such function is invoked only by a timer, so we are guaranteeded there are no possible concurrent updates...n->keepalive_intv = 10000; - tipc_node_read_unlock(n); + tipc_node_write_unlock(n); for (bearer_id = 0; remains && (bearer_id < MAX_BEARERS); bearer_id++) { tipc_node_read_lock(n);...otherwise we have a similar issue here: a few line below keepalive_intv is updated via tipc_node_calculate_timer(), still under the read lock Thanks! Paolo
Hoang's and Paolo's conclusion is correct. The patch is not needed. ///jon _______________________________________________ tipc-discussion mailing list tipc-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/tipc-discussion
