linux-kernel - [PATCH 5.19 152/365] fscache: dont leak cookie access refs if invalidation is in progress or failed

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Date:   Tue, 23 Aug 2022 10:00:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Howells <dhowells@...hat.com>,
        Jeff Layton <jlayton@...nel.org>
Subject: [PATCH 5.19 152/365] fscache: dont leak cookie access refs if invalidation is in progress or failed

From: Jeff Layton <jlayton@...nel.org>

commit fb24771faf72a2fd62b3b6287af3c610c3ec9cf1 upstream.

It's possible for a request to invalidate a fscache_cookie will come in
while we're already processing an invalidation. If that happens we
currently take an extra access reference that will leak. Only call
__fscache_begin_cookie_access if the FSCACHE_COOKIE_DO_INVALIDATE bit
was previously clear.

Also, ensure that we attempt to clear the bit when the cookie is
"FAILED" and put the reference to avoid an access leak.

Fixes: 85e4ea1049c7 ("fscache: Fix invalidation/lookup race")
Suggested-by: David Howells <dhowells@...hat.com>
Signed-off-by: Jeff Layton <jlayton@...nel.org>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/fscache/cookie.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 74920826d8f6..26a6d395737a 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -739,6 +739,9 @@ static void fscache_cookie_state_machine(struct fscache_cookie *cookie)
 		fallthrough;
 
 	case FSCACHE_COOKIE_STATE_FAILED:
+		if (test_and_clear_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
+			fscache_end_cookie_access(cookie, fscache_access_invalidate_cookie_end);
+
 		if (atomic_read(&cookie->n_accesses) != 0)
 			break;
 		if (test_bit(FSCACHE_COOKIE_DO_RELINQUISH, &cookie->flags)) {
@@ -1063,8 +1066,8 @@ void __fscache_invalidate(struct fscache_cookie *cookie,
 		return;
 
 	case FSCACHE_COOKIE_STATE_LOOKING_UP:
-		__fscache_begin_cookie_access(cookie, fscache_access_invalidate_cookie);
-		set_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags);
+		if (!test_and_set_bit(FSCACHE_COOKIE_DO_INVALIDATE, &cookie->flags))
+			__fscache_begin_cookie_access(cookie, fscache_access_invalidate_cookie);
 		fallthrough;
 	case FSCACHE_COOKIE_STATE_CREATING:
 		spin_unlock(&cookie->lock);
-- 
2.37.2