[patch 31/30] bsdacct: fix access to invalid filp in acct_on()

From: Greg KH
Date: Wed Jul 01 2009 - 14:38:42 EST



2.6.27-stable review patch

----------------

From: Renaud Lottiaux <renaud.lottiaux@xxxxxxxxxxx>

commit df279ca8966c3de83105428e3391ab17690802a9 upstream.

The file opened in acct_on and freshly stored in the ns->bacct struct can
be closed in acct_file_reopen by a concurrent call after we release
acct_lock and before we call mntput(file->f_path.mnt).

Record file->f_path.mnt in a local variable and use this variable only.

Signed-off-by: Renaud Lottiaux <renaud.lottiaux@xxxxxxxxxxx>
Signed-off-by: Louis Rilling <louis.rilling@xxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
kernel/acct.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/kernel/acct.c
+++ b/kernel/acct.c
@@ -215,6 +215,7 @@ static void acct_file_reopen(struct bsd_
static int acct_on(char *name)
{
struct file *file;
+ struct vfsmount *mnt;
int error;
struct pid_namespace *ns;
struct bsd_acct_struct *acct = NULL;
@@ -256,11 +257,12 @@ static int acct_on(char *name)
acct = NULL;
}

- mnt_pin(file->f_path.mnt);
+ mnt = file->f_path.mnt;
+ mnt_pin(mnt);
acct_file_reopen(ns->bacct, file, ns);
spin_unlock(&acct_lock);

- mntput(file->f_path.mnt); /* it's pinned, now give up active reference */
+ mntput(mnt); /* it's pinned, now give up active reference */
kfree(acct);

return 0;
--
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