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Subject[PATCH] fs: ocfs2: dlm: Fix a sleep-in-atomic-context bug in dlm_print_one_mle()
Date
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@gmail.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
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