[PATCH 3.2 49/79] autofs4: autofs4_wait() vs. autofs4_catatonic_mode() race

Ben Hutchings
2018-02-11T04:33:41Z

From: Al Viro <viro@zeniv.linux.org.uk>

commit 4041bcdc7bef06a2fb29c57394c713a74bd13b08 upstream.

We need to recheck ->catatonic after autofs4_wait() got ->wq_mutex
for good, or we might end up with wq inserted into queue after
autofs4_catatonic_mode() had done its thing. It will stick there
forever, since there won't be anything to clear its ->name.name.

A bit of a complication: validate_request() drops and regains ->wq_mutex.
It actually ends up the most convenient place to stick the check into...

Acked-by: Ian Kent <raven@themaw.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/autofs4/waitq.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -257,6 +257,9 @@ static int validate_request(struct autof
struct autofs_wait_queue *wq;
struct autofs_info *ino;

+ if (sbi->catatonic)
+ return -ENOENT;
+
/* Wait in progress, continue; */
wq = autofs4_find_wait(sbi, qstr);
if (wq) {
@@ -289,6 +292,9 @@ static int validate_request(struct autof
if (mutex_lock_interruptible(&sbi->wq_mutex))
return -EINTR;

+ if (sbi->catatonic)
+ return -ENOENT;
+
wq = autofs4_find_wait(sbi, qstr);
if (wq) {
*wait = wq;
@@ -389,7 +395,7 @@ int autofs4_wait(struct autofs_sb_info *

ret = validate_request(&wq, sbi, &qstr, dentry, notify);
if (ret <= 0) {
- if (ret == 0)
+ if (ret != -EINTR)
mutex_unlock(&sbi->wq_mutex);
kfree(qstr.name);
return ret;