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autofs4: close the races around autofs4_notify_daemon() 

Don't drop ->wq_mutex before calling autofs4_notify_daemon() only to regain it
there.  Besides being pointless, that opens a race window where autofs4_wait_release()
could've come and freed wq->name.name.  And do the debugging printk in the "reused an
existing wq" case before dropping ->wq_mutex - the same reason...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Ian Kent <raven@themaw.net>
This commit is contained in:
Al Viro 2013-09-14 17:32:12 -04:00
parent 3711d86a2d
commit 606035e76e
1 changed files with 3 additions and 10 deletions
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13
fs/autofs4/waitq.c
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@ -109,13 +109,7 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi,
pkt.hdr.proto_version = sbi->version;
pkt.hdr.type = type;
mutex_lock(&sbi->wq_mutex);
/* Check if we have become catatonic */
if (sbi->catatonic) {
mutex_unlock(&sbi->wq_mutex);
return;
}
switch (type) {
/* Kernel protocol v4 missing and expire packets */
case autofs_ptype_missing:
@ -427,7 +421,6 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
wq->tgid = current->tgid;
wq->status = -EINTR; /* Status return if interrupted */
wq->wait_ctr = 2;
mutex_unlock(&sbi->wq_mutex);
if (sbi->version < 5) {
if (notify == NFY_MOUNT)
@ -449,15 +442,15 @@ int autofs4_wait(struct autofs_sb_info *sbi, struct dentry *dentry,
(unsigned long) wq->wait_queue_token, wq->name.len,
wq->name.name, notify);
/* autofs4_notify_daemon() may block */
/* autofs4_notify_daemon() may block; it will unlock ->wq_mutex */
autofs4_notify_daemon(sbi, wq, type);
} else {
wq->wait_ctr++;
mutex_unlock(&sbi->wq_mutex);
kfree(qstr.name);
DPRINTK("existing wait id = 0x%08lx, name = %.*s, nfy=%d",
(unsigned long) wq->wait_queue_token, wq->name.len,
wq->name.name, notify);
mutex_unlock(&sbi->wq_mutex);
kfree(qstr.name);
}
/*