From: Eric W. Biederman Date: Thu, 13 Sep 2007 07:18:57 +0000 (+0200) Subject: [NET]: Fix race when opening a proc file while a network namespace is exiting. X-Git-Tag: v2.6.24-rc1~1454^2~675 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=077130c0cf7d5ba1992f5b51b96136d7b1c8aad5;p=pandora-kernel.git [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 Acked-by: Paul E. McKenney Signed-off-by: David S. Miller --- Reading git-diff-tree failed