diff options
author | Christian Borntraeger <borntraeger@de.ibm.com> | 2009-03-23 17:51:17 -0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-05-02 10:57:02 -0700 |
commit | 38a9de467cba9d691a22fe689b759fad0dec4d69 (patch) | |
tree | e8e857a509d6f39bc646f17b53d8c199a62dc9f9 | |
parent | 7f871d00b7b32cafb8800a45b1d4eca94479deff (diff) |
anon_inodes: use fops->owner for module refcount
There is an imbalance for anonymous inodes. If the fops->owner field is set,
the module reference count of owner is decreases on release.
("filp_close" --> "__fput" ---> "fops_put")
On the other hand, anon_inode_getfd does not increase the module reference
count of owner. This causes two problems:
- if owner is set, the module refcount goes negative
- if owner is not set, the module can be unloaded while code is running
This patch changes anon_inode_getfd to be symmetric regarding fops->owner
handling.
I have checked all existing users of anon_inode_getfd. Noone sets fops->owner,
thats why nobody has seen the module refcount negative. The refcounting was
tested with a patched and unpatched KVM module.(see patch 2/2) I also did an
epoll_open/close test.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Avi Kivity <avi@redhat.com>
(cherry picked from commit e3a2a0d4e5ace731e60e2eff4fb7056ecb34adc1)
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r-- | fs/anon_inodes.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c index 3662dd44896b..96bbafbddc35 100644 --- a/fs/anon_inodes.c +++ b/fs/anon_inodes.c @@ -79,9 +79,12 @@ int anon_inode_getfd(const char *name, const struct file_operations *fops, if (IS_ERR(anon_inode_inode)) return -ENODEV; + if (fops->owner && !try_module_get(fops->owner)) + return -ENOENT; + error = get_unused_fd_flags(flags); if (error < 0) - return error; + goto err_module; fd = error; /* @@ -128,6 +131,8 @@ err_dput: dput(dentry); err_put_unused_fd: put_unused_fd(fd); +err_module: + module_put(fops->owner); return error; } EXPORT_SYMBOL_GPL(anon_inode_getfd); |