From: Andrei Tatar <andrei@unikraft.io>
Date: Fri, 21 Mar 2025 09:44:00 +0000 (+0100)
Subject: lib/posix-fdtab: Fix ref leak on fdtab clone
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=f1587f236275f00dbff1f34fb4523b8ff509d1aa;p=unikraft%2Funikraft.git

lib/posix-fdtab: Fix ref leak on fdtab clone

This change adds a missing ref release of the previous fdtab instance on
clone, leading to a reference (and thus memory) leak with multi-fdtab.

Signed-off-by: Andrei Tatar <andrei@unikraft.io>
Approved-by: Michalis Pappas <michalis@unikraft.io>
Reviewed-by: Michalis Pappas <michalis@unikraft.io>
GitHub-Closes: #1617
---

diff --git a/lib/posix-fdtab/fdtab.c b/lib/posix-fdtab/fdtab.c
index 2e607546b..b3e91b792 100644
--- a/lib/posix-fdtab/fdtab.c
+++ b/lib/posix-fdtab/fdtab.c
@@ -485,9 +485,15 @@ static int fdtab_clone(const struct clone_args *cl_args,
 		return 0;
 	} else {
 		/* Duplicate parent's fdtab */
+		int r __maybe_unused;
+
 		newtab = fdtab_duplicate(tab);
 		if (unlikely(!newtab))
 			return -ENOMEM;
+		/* Compat stop-gap: release previous duplicate ref */
+		UK_ASSERT(uk_thread_uktls_var(child, active_fdtab) == tab);
+		r = uk_refcount_release(&tab->refcnt);
+		UK_ASSERT(!r); /* Cannot have been the last ref */
 	}
 	uk_thread_uktls_var(child, active_fdtab) = newtab;
 	return 0;