netdev - [PATCH iproute2 v2 2/2] lib/fs: Fix single return points for get_cgroup2

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Date:   Mon, 22 Feb 2021 19:14:32 +0100
From:   Andrea Claudi <aclaudi@...hat.com>
To:     netdev@...r.kernel.org
Cc:     stephen@...workplumber.org, dsahern@...il.com
Subject: [PATCH iproute2 v2 2/2] lib/fs: Fix single return points for get_cgroup2_*

Functions get_cgroup2_id() and get_cgroup2_path() may call close() with
a negative argument.
Avoid that making the calls conditional on the file descriptors.

get_cgroup2_path() may also return NULL leaking a file descriptor.
Ensure this does not happen using a single return point.

Fixes: d5e6ee0dac64 ("ss: introduce cgroup2 cache and helper functions")
Fixes: 8f1cd119b377 ("lib: fix checking of returned file handle size for cgroup")
Signed-off-by: Andrea Claudi <aclaudi@...hat.com>
---
 lib/fs.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/lib/fs.c b/lib/fs.c
index 2ae506ec..ee0b130b 100644
--- a/lib/fs.c
+++ b/lib/fs.c
@@ -157,7 +157,8 @@ __u64 get_cgroup2_id(const char *path)
 	memcpy(cg_id.bytes, fhp->f_handle, sizeof(__u64));
 
 out:
-	close(mnt_fd);
+	if (mnt_fd >= 0)
+		close(mnt_fd);
 	free(mnt);
 
 	return cg_id.id;
@@ -179,16 +180,16 @@ char *get_cgroup2_path(__u64 id, bool full)
 	char *path = NULL;
 	char fd_path[64];
 	int link_len;
-	char *mnt;
+	char *mnt = NULL;
 
 	if (!id) {
 		fprintf(stderr, "Invalid cgroup2 ID\n");
-		return NULL;
+		goto out;
 	}
 
 	mnt = find_cgroup2_mount(false);
 	if (!mnt)
-		return NULL;
+		goto out;
 
 	mnt_fd = open(mnt, O_RDONLY);
 	if (mnt_fd < 0) {
@@ -225,8 +226,10 @@ char *get_cgroup2_path(__u64 id, bool full)
 			"Failed to allocate memory for cgroup2 path\n");
 
 out:
-	close(fd);
-	close(mnt_fd);
+	if (fd >= 0)
+		close(fd);
+	if (mnt_fd >= 0)
+		close(mnt_fd);
 	free(mnt);
 
 	return path;
-- 
2.29.2