Fix UTS corruption during clone(CLONE_NEWUTS)

struct utsname is copied from master one without any exclusion.

Here is sample output from one proggie doing

	sethostname("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
	sethostname("bbbbbbbbbbbbbbbbbbbbbbbbbbbbbb");

and another

	clone(,, CLONE_NEWUTS, ...)
	uname()

	hostname = 'aaaaaaaaaaaaaaaaaaaaaaaaabbbbb'
	hostname = 'bbbaaaaaaaaaaaaaaaaaaaaaaaaaaa'
	hostname = 'aaaaaaaabbbbbbbbbbbbbbbbbbbbbb'
	hostname = 'aaaaaaaaaaaaaaaaaaaaaaaaaabbbb'
	hostname = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaabb'
	hostname = 'aaabbbbbbbbbbbbbbbbbbbbbbbbbbb'
	hostname = 'bbbbbbbbbbbbbbbbaaaaaaaaaaaaaa'

Hostname is sometimes corrupted.

Yes, even _the_ simplest namespace activity had bug in it. :-(

Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/utsname.c b/kernel/utsname.c
index 9d8180a0f0d815dbe051dbb6a710385d22f0b342..816d7b24fa031af51b08d9108366d21626e3d38e 100644 (file)
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -28,7 +28,9 @@ static struct uts_namespace *clone_uts_ns(struct uts_namespace *old_ns)
        if (!ns)
                return ERR_PTR(-ENOMEM);
 
+       down_read(&uts_sem);
        memcpy(&ns->name, &old_ns->name, sizeof(ns->name));
+       up_read(&uts_sem);
        kref_init(&ns->kref);
        return ns;
 }