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* [PATCH] cgroup: fix cgroup_path() vs rename() race
@ 2013-01-25  7:09 Li Zefan
       [not found] ` <51022FC7.5020607-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
  0 siblings, 1 reply; 5+ messages in thread
From: Li Zefan @ 2013-01-25  7:09 UTC (permalink / raw)
  To: Tejun Heo; +Cc: Al Viro, LKML, Cgroups

rename() will change dentry->d_name. The result of this race can
be worse than seeing partially rewritten name, but we might access
a stale pointer because rename() will re-allocate memory to hold
a longer name.

Use dentry_path_raw(), and this vfs API will take care of lockings.

Signed-off-by: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
---
 kernel/cgroup.c | 22 +++-------------------
 1 file changed, 3 insertions(+), 19 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5d4c92e..776ff75 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1792,26 +1792,10 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
 		return 0;
 	}
 
-	start = buf + buflen - 1;
+	start = dentry_path_raw(dentry, buf, buflen);
+	if (IS_ERR(start))
+		return PTR_ERR(start);
 
-	*start = '\0';
-	for (;;) {
-		int len = dentry->d_name.len;
-
-		if ((start -= len) < buf)
-			return -ENAMETOOLONG;
-		memcpy(start, dentry->d_name.name, len);
-		cgrp = cgrp->parent;
-		if (!cgrp)
-			break;
-
-		dentry = cgrp->dentry;
-		if (!cgrp->parent)
-			continue;
-		if (--start < buf)
-			return -ENAMETOOLONG;
-		*start = '/';
-	}
 	memmove(buf, start, buf + buflen - start);
 	return 0;
 }
-- 
1.8.0.2

^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2013-02-16  7:59 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-01-25  7:09 [PATCH] cgroup: fix cgroup_path() vs rename() race Li Zefan
     [not found] ` <51022FC7.5020607-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2013-01-25 16:42   ` Tejun Heo
     [not found]     ` <20130125164242.GA3081-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2013-01-26  0:20       ` Li Zefan
2013-02-08 18:46   ` Sasha Levin
     [not found]     ` <511547EA.4090902-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2013-02-16  7:59       ` Li Zefan

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