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authorSerge E. Hallyn <serue@us.ibm.com>2007-01-29 13:19:40 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-01-30 08:26:44 -0800
commit7a238fcba0629b6f2edbcd37458bae56fcf36be5 (patch)
treead556f0ec00637df5b4c4a2063c6b3325666d2f1 /include
parentc0d4d573feed199b16094c072e7cb07afb01c598 (diff)
[PATCH] namespaces: fix exit race by splitting exit
Fix exit race by splitting the nsproxy putting into two pieces. First piece reduces the nsproxy refcount. If we dropped the last reference, then it puts the mnt_ns, and returns the nsproxy as a hint to the caller. Else it returns NULL. The second piece of exiting task namespaces sets tsk->nsproxy to NULL, and drops the references to other namespaces and frees the nsproxy only if an nsproxy was passed in. A little awkward and should probably be reworked, but hopefully it fixes the NFS oops. Signed-off-by: Serge E. Hallyn <serue@us.ibm.com> Cc: Herbert Poetzl <herbert@13thfloor.at> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Cedric Le Goater <clg@fr.ibm.com> Cc: Daniel Hokka Zakrisson <daniel@hozac.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/nsproxy.h30
1 files changed, 19 insertions, 11 deletions
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index 0b9f0dc30d61..678e1d38effb 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -35,22 +35,30 @@ struct nsproxy *dup_namespaces(struct nsproxy *orig);
int copy_namespaces(int flags, struct task_struct *tsk);
void get_task_namespaces(struct task_struct *tsk);
void free_nsproxy(struct nsproxy *ns);
+struct nsproxy *put_nsproxy(struct nsproxy *ns);
-static inline void put_nsproxy(struct nsproxy *ns)
+static inline void finalize_put_nsproxy(struct nsproxy *ns)
{
- if (atomic_dec_and_test(&ns->count)) {
+ if (ns)
free_nsproxy(ns);
- }
}
-static inline void exit_task_namespaces(struct task_struct *p)
+static inline void put_and_finalize_nsproxy(struct nsproxy *ns)
{
- struct nsproxy *ns = p->nsproxy;
- if (ns) {
- task_lock(p);
- p->nsproxy = NULL;
- task_unlock(p);
- put_nsproxy(ns);
- }
+ finalize_put_nsproxy(put_nsproxy(ns));
+}
+
+static inline struct nsproxy *preexit_task_namespaces(struct task_struct *p)
+{
+ return put_nsproxy(p->nsproxy);
+}
+
+static inline void exit_task_namespaces(struct task_struct *p,
+ struct nsproxy *ns)
+{
+ task_lock(p);
+ p->nsproxy = NULL;
+ task_unlock(p);
+ finalize_put_nsproxy(ns);
}
#endif