linux-kernel - [PATCH] cgroup: add explicit cast and comment for return type conversion

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Sun, 24 May 2015 15:07:52 +0200
From:	Nicholas Mc Guire <hofrat@...dl.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	Li Zefan <lizefan@...wei.com>, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, Nicholas Mc Guire <hofrat@...dl.org>
Subject: [PATCH] cgroup: add explicit cast and comment for return type conversion

Type-checking coccinelle spatches are being used to locate type mismatches
between function signatures and return values in this case this produced:
./kernel/cgroup.c:2525 WARNING: return of wrong type
	ssize_t != size_t, 

Returning unsigned types converted to a signed type can be problematic
but in this case the size_t is <= PATH_MAX which is less than ulong/2 so
the conversion is safe - to make static code checking happy this is 
resolved by an explicit cast and appropriate comment.

Patch was compile tested with x86_64_defconfig (implies CONFIG_CGROUPS=y)

Patch is against 4.1-rc4 (localversion-next is -next-20150522)

Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
---

Not sure if "cleanups" like this are acceptable - in this case I did not
find any better way to make static code checkers happy though.

 kernel/cgroup.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b91177f..04de621 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2523,7 +2523,11 @@ static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
 		sizeof(cgrp->root->release_agent_path));
 	spin_unlock(&release_agent_path_lock);
 	cgroup_kn_unlock(of->kn);
-	return nbytes;
+
+	/* the path of the release notifier is <= PATH_MAX
+	 * so "downsizing" to signed long is safe here
+	 */
+	return (ssize_t)nbytes;
 }
 
 static int cgroup_release_agent_show(struct seq_file *seq, void *v)
-- 
1.7.10.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/