diff options
author | Eric W. Biederman <ebiederm@xmission.com> | 2007-09-13 07:18:57 (GMT) |
---|---|---|
committer | David S. Miller <davem@sunset.davemloft.net> | 2007-10-10 23:49:22 (GMT) |
commit | 077130c0cf7d5ba1992f5b51b96136d7b1c8aad5 (patch) | |
tree | c8fd2622e7d633cc504c7543b55e25bd6d99a2fa /net/core | |
parent | 4fabcd7118162e36eea5c53e8895ecc13762bef3 (diff) | |
download | linux-fsl-qoriq-077130c0cf7d5ba1992f5b51b96136d7b1c8aad5.tar.xz |
[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 'net/core')
-rw-r--r-- | net/core/dev.c | 6 | ||||
-rw-r--r-- | net/core/dev_mcast.c | 6 |
2 files changed, 10 insertions, 2 deletions
diff --git a/net/core/dev.c b/net/core/dev.c index d16dcab..666c112 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2464,7 +2464,11 @@ static int dev_seq_open(struct inode *inode, struct file *file) res = seq_open(file, &dev_seq_ops); if (!res) { seq = file->private_data; - seq->private = get_net(PROC_NET(inode)); + seq->private = get_proc_net(inode); + if (!seq->private) { + seq_release(inode, file); + res = -ENXIO; + } } return res; } diff --git a/net/core/dev_mcast.c b/net/core/dev_mcast.c index 1c4f619..896b0ca 100644 --- a/net/core/dev_mcast.c +++ b/net/core/dev_mcast.c @@ -246,7 +246,11 @@ static int dev_mc_seq_open(struct inode *inode, struct file *file) res = seq_open(file, &dev_mc_seq_ops); if (!res) { seq = file->private_data; - seq->private = get_net(PROC_NET(inode)); + seq->private = get_proc_net(inode); + if (!seq->private) { + seq_release(inode, file); + res = -ENXIO; + } } return res; } |