The timer ID stored in ka->timer uses -1 as the sentinel value meaning 'not initialized' (set in virKeepAliveNew). The checks in virKeepAliveStop and virKeepAliveDispose used '> 0' or '>= 0' to determine whether a timer is active. However, if nexttimer overflows (see previous fix in vireventglib.c), ka->timer can be a negative value other than -1 (e.g., -2147483648). In that case: - 'if (ka->timer > 0)' returns false -> virEventRemoveTimeout skipped - 'if (ka->timer >= 0)' returns false -> virEventRemoveTimeout skipped This leaves the GSource active after the keepalive object is freed, causing a use-after-free with 'bad magic number' warnings in the log. Fix by changing the checks to 'if (ka->timer != -1)', which correctly handles both positive and negative timer IDs while still skipping the sentinel value -1. Additionally, add the same check in virKeepAliveDispose as a safety net: if the object's refcount reaches 0 due to a race condition or reference counting bug, the timer must be stopped before the object is freed. Signed-off-by: Yong Chen <410664530@qq.com> --- src/rpc/virkeepalive.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/src/rpc/virkeepalive.c b/src/rpc/virkeepalive.c index 690bc08b2e..4e7dd25d3c 100644 --- a/src/rpc/virkeepalive.c +++ b/src/rpc/virkeepalive.c @@ -218,6 +218,18 @@ virKeepAliveDispose(void *obj) PROBE(RPC_KEEPALIVE_DISPOSE, "ka=%p", ka); + /* Ensure the timer is stopped before freeing the object. + * This is a safety net: normally virKeepAliveStop is called + * before the object's refcount reaches 0, but in case of + * race conditions or reference counting bugs, we must not + * leave a dangling timer that would trigger use-after-free. + * Use != -1 (not >= 0) to also handle negative timer IDs + * caused by nexttimer integer overflow. */ + if (ka->timer != -1) { + virEventRemoveTimeout(ka->timer); + ka->timer = -1; + } + ka->freeCB(ka->client); } @@ -301,7 +313,7 @@ virKeepAliveStop(virKeepAlive *ka) "ka=%p client=%p", ka, ka->client); - if (ka->timer > 0) { + if (ka->timer ！= -1) { virEventRemoveTimeout(ka->timer); ka->timer = -1; } -- 2.55.0.windows.3