linux-kernel - [PATCH] fs/afs/flock and fs/locks: Fix possible sleep-in-atomic bugs in posix_lock

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Date:   Sat,  7 Oct 2017 17:55:04 +0800
From:   Jia-Ju Bai <baijiaju1990@....com>
To:     dhowells@...hat.com, viro@...iv.linux.org.uk,
        jlayton@...chiereds.net, bfields@...ldses.org
Cc:     linux-fsdevel@...r.kernel.org, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju1990@....com>
Subject: [PATCH] fs/afs/flock and fs/locks: Fix possible sleep-in-atomic bugs in posix_lock_file 

The kernel may sleep under a spinlock, and the function call paths are:
afs_do_unlk (acquire the spinlock)
  posix_lock_file
    posix_lock_inode (fs/locks.c)
      locks_get_lock_context
        kmem_cache_alloc(GFP_KERNEL) --> may sleep

afs_do_setlk (acquire the spinlock)
  posix_lock_file
    posix_lock_inode (fs/locks.c)
      locks_get_lock_context
        kmem_cache_alloc(GFP_KERNEL) --> may sleep

To fix them, GFP_KERNEL is replaced with GFP_ATOMIC.
These bugs are found by my static analysis tool and my code review.

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

diff --git a/fs/locks.c b/fs/locks.c
index 1bd71c4..975cc62 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -222,7 +222,7 @@ struct file_lock_list_struct {
 	if (likely(ctx) || type == F_UNLCK)
 		goto out;
 
-	ctx = kmem_cache_alloc(flctx_cache, GFP_KERNEL);
+	ctx = kmem_cache_alloc(flctx_cache, GFP_ATOMIC);
 	if (!ctx)
 		goto out;
 
-- 
1.7.9.5