linux-kernel - [PATCH] fs: ocfs2: dlm: Fix a sleep-in-atomic-context bug in dlm_print_one

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Date:   Sat,  1 Sep 2018 19:25:28 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     mark@...heh.com, jlbec@...lplan.org
Cc:     ocfs2-devel@....oracle.com, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] fs: ocfs2: dlm: Fix a sleep-in-atomic-context bug in dlm_print_one_mle()

The kernel module may sleep with holding a spinlock.

The function call paths (from bottom to top) in Linux-4.16 are:

[FUNC] get_zeroed_page(GFP_NOFS)
fs/ocfs2/dlm/dlmdebug.c, 332: get_zeroed_page in dlm_print_one_mle
fs/ocfs2/dlm/dlmmaster.c, 240: dlm_print_one_mle in __dlm_put_mle
fs/ocfs2/dlm/dlmmaster.c, 255: __dlm_put_mle in dlm_put_mle
fs/ocfs2/dlm/dlmmaster.c, 254: spin_lock in dlm_put_ml

[FUNC] get_zeroed_page(GFP_NOFS)
fs/ocfs2/dlm/dlmdebug.c, 332: get_zeroed_page in dlm_print_one_mle
fs/ocfs2/dlm/dlmmaster.c, 240: dlm_print_one_mle in __dlm_put_mle
fs/ocfs2/dlm/dlmmaster.c, 222: __dlm_put_mle in dlm_put_mle_inuse
fs/ocfs2/dlm/dlmmaster.c, 219: spin_lock in dlm_put_mle_inuse

To fix this bug, GFP_NOFS is replaced with GFP_ATOMIC.

This bug is found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 fs/ocfs2/dlm/dlmdebug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ocfs2/dlm/dlmdebug.c b/fs/ocfs2/dlm/dlmdebug.c
index 9b984cae4c4e..1d6dc8422899 100644
--- a/fs/ocfs2/dlm/dlmdebug.c
+++ b/fs/ocfs2/dlm/dlmdebug.c
@@ -329,7 +329,7 @@ void dlm_print_one_mle(struct dlm_master_list_entry *mle)
 {
 	char *buf;
 
-	buf = (char *) get_zeroed_page(GFP_NOFS);
+	buf = (char *) get_zeroed_page(GFP_ATOMIC);
 	if (buf) {
 		dump_mle(mle, buf, PAGE_SIZE - 1);
 		free_page((unsigned long)buf);
-- 
2.17.0