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fs/proc: fix potential unregister_sysctl_table hang

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The unregister_sysctl_table() function hangs if all references to its
ctl_table_header structure are not dropped.

This can happen sometimes because of a leak in proc_sys_lookup():
proc_sys_lookup() gets a reference to the table via lookup_entry(), but
it does not release it when a subsequent call to sysctl_follow_link()
fails.

This patch fixes this leak by making sure the reference is always
dropped on return.

See also commit 076c3eed2c ("sysctl: Rewrite proc_sys_lookup
introducing find_entry and lookup_entry") which reorganized this code in
3.4.

Tested in Linux 3.4.4.

Signed-off-by: Francesco Ruggeri <fruggeri@aristanetworks.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Francesco Ruggeri 2012-09-13 15:03:37 -07:00 committed by Linus Torvalds
parent 5698bd757d
commit 6bf6104573
1 changed files with 2 additions and 3 deletions
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5
fs/proc/proc_sysctl.c
View file

@ -462,9 +462,6 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
err = ERR_PTR(-ENOMEM);
inode = proc_sys_make_inode(dir->i_sb, h ? h : head, p);
if (h)
sysctl_head_finish(h);
if (!inode)
goto out;
@ -473,6 +470,8 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,
d_add(dentry, inode);
out:
if (h)
sysctl_head_finish(h);
sysctl_head_finish(head);
return err;
}