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authorEric W. Biederman <ebiederm@xmission.com>2007-09-13 09:18:57 +0200
committerDavid S. Miller <davem@sunset.davemloft.net>2007-10-10 16:49:22 -0700
commit077130c0cf7d5ba1992f5b51b96136d7b1c8aad5 (patch)
treec8fd2622e7d633cc504c7543b55e25bd6d99a2fa /include/linux
parent4fabcd7118162e36eea5c53e8895ecc13762bef3 (diff)
[NET]: Fix race when opening a proc file while a network namespace is exiting.
The problem: proc_net files remember which network namespace the are against but do not remember hold a reference count (as that would pin the network namespace). So we currently have a small window where the reference count on a network namespace may be incremented when opening a /proc file when it has already gone to zero. To fix this introduce maybe_get_net and get_proc_net. maybe_get_net increments the network namespace reference count only if it is greater then zero, ensuring we don't increment a reference count after it has gone to zero. get_proc_net handles all of the magic to go from a proc inode to the network namespace instance and call maybe_get_net on it. PROC_NET the old accessor is removed so that we don't get confused and use the wrong helper function. Then I fix up the callers to use get_proc_net and handle the case case where get_proc_net returns NULL. In that case I return -ENXIO because effectively the network namespace has already gone away so the files we are trying to access don't exist anymore. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Acked-by: Paul E. McKenney <paulmck@us.ibm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/proc_fs.h5
1 files changed, 1 insertions, 4 deletions
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 59646705f15..20741f668f7 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -270,10 +270,7 @@ static inline struct net *PDE_NET(struct proc_dir_entry *pde)
return pde->parent->data;
}
-static inline struct net *PROC_NET(const struct inode *inode)
-{
- return PDE_NET(PDE(inode));
-}
+struct net *get_proc_net(const struct inode *inode);
struct proc_maps_private {
struct pid *pid;