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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 /kernel
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 'kernel')
-rw-r--r--kernel/exit.c6
-rw-r--r--kernel/fork.c4
-rw-r--r--kernel/nsproxy.c16
3 files changed, 21 insertions, 5 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 35401720635..a5bf5329ff9 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -396,7 +396,7 @@ void daemonize(const char *name, ...)
current->fs = fs;
atomic_inc(&fs->count);
- exit_task_namespaces(current);
+ put_and_finalize_nsproxy(current->nsproxy);
current->nsproxy = init_task.nsproxy;
get_task_namespaces(current);
@@ -853,6 +853,7 @@ static void exit_notify(struct task_struct *tsk)
fastcall NORET_TYPE void do_exit(long code)
{
struct task_struct *tsk = current;
+ struct nsproxy *ns;
int group_dead;
profile_task_exit(tsk);
@@ -938,8 +939,9 @@ fastcall NORET_TYPE void do_exit(long code)
tsk->exit_code = code;
proc_exit_connector(tsk);
+ ns = preexit_task_namespaces(tsk);
exit_notify(tsk);
- exit_task_namespaces(tsk);
+ exit_task_namespaces(tsk, ns);
#ifdef CONFIG_NUMA
mpol_free(tsk->mempolicy);
tsk->mempolicy = NULL;
diff --git a/kernel/fork.c b/kernel/fork.c
index fc723e595cd..4cf868458f0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1265,7 +1265,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
return p;
bad_fork_cleanup_namespaces:
- exit_task_namespaces(p);
+ put_and_finalize_nsproxy(p->nsproxy);
bad_fork_cleanup_keys:
exit_keys(p);
bad_fork_cleanup_mm:
@@ -1711,7 +1711,7 @@ asmlinkage long sys_unshare(unsigned long unshare_flags)
}
if (new_nsproxy)
- put_nsproxy(new_nsproxy);
+ put_and_finalize_nsproxy(new_nsproxy);
bad_unshare_cleanup_ipc:
if (new_ipc)
diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f5b9ee6f6bb..7b05bce75cd 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -117,7 +117,7 @@ int copy_namespaces(int flags, struct task_struct *tsk)
goto out_pid;
out:
- put_nsproxy(old_ns);
+ put_and_finalize_nsproxy(old_ns);
return err;
out_pid:
@@ -135,6 +135,20 @@ out_ns:
goto out;
}
+struct nsproxy *put_nsproxy(struct nsproxy *ns)
+{
+ if (ns) {
+ if (atomic_dec_and_test(&ns->count)) {
+ if (ns->mnt_ns) {
+ put_mnt_ns(ns->mnt_ns);
+ ns->mnt_ns = NULL;
+ }
+ return ns;
+ }
+ }
+ return NULL;
+}
+
void free_nsproxy(struct nsproxy *ns)
{
if (ns->mnt_ns)