TheArchive/tailscale
1
0
Fork 0
mirror of https://github.com/tailscale/tailscale.git synced 2025-10-29 07:09:33 +00:00
Code Issues Packages Projects Releases Wiki Activity

ipn/ipnserver: fix a deadlock in (*Server).blockWhileIdentityInUse

Browse Source 
If the server was in use at the time of the initial check, but disconnected and was removed
from the activeReqs map by the time we registered a waiter, the ready channel will never
be closed, resulting in a deadlock. To avoid this, we check whether the server is still busy
after registering the wait.

Fixes #14655

Signed-off-by: Nick Khyl <nickk@tailscale.com>
This commit is contained in:
Nick Khyl
2025-01-15 16:03:21 -06:00
committed by Nick Khyl
parent 62fb857857
commit 0481042738
2 changed files with 58 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
ipn/ipnserver/server.go
View File

@@ -283,7 +283,18 @@ func (s *Server) blockWhileIdentityInUse(ctx context.Context, actor ipnauth.Acto
for inUse() {
// Check whenever the connection count drops down to zero.
ready, cleanup := s.zeroReqWaiter.add(&s.mu, ctx)
<-ready
if inUse() {
// If the server was in use at the time of the initial check,
// but disconnected and was removed from the activeReqs map
// by the time we registered a waiter, the ready channel
// will never be closed, resulting in a deadlock. To avoid
// this, we can check again after registering the waiter.
//
// This method is planned for complete removal as part of the
// multi-user improvements in tailscale/corp#18342,
// and this approach should be fine as a temporary solution.
<-ready
}
cleanup()
if err := ctx.Err(); err != nil {
return err