[PATCH] fork.c: fix NULL pointer dereference when nr_threads == threads-max

From: Li Zefan
Date: Thu Feb 05 2009 - 20:15:22 EST


I happened to forked lots of processes, and hit NULL pointer dereference.
It is because in copy_process() after checking max_threads, 0 is returned
but not -EAGAIN.

The bug is introduced by this patch:

| commit f1752eec6145c97163dbce62d17cf5d928e28a27
| Author: David Howells <dhowells@xxxxxxxxxx>
| Date: Fri Nov 14 10:39:17 2008 +1100
|
| CRED: Detach the credentials from task_struct

Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
---
kernel/fork.c | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 242a706..6d5dbb7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1005,6 +1005,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
* triggers too late. This doesn't hurt, the check is only there
* to stop root fork bombs.
*/
+ retval = -EAGAIN;
if (nr_threads >= max_threads)
goto bad_fork_cleanup_count;

--
1.5.4.rc3

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