linux-kernel - [PATCH] fs: jffs2: fix a sleep-in-atomic-context bug in jffs2_alloc

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Date:   Mon, 13 Aug 2018 11:25:47 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     dwmw2@...radead.org
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] fs: jffs2: fix a sleep-in-atomic-context bug in jffs2_alloc_refblock()

The kernel may sleep with holding a spin lock.

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

[FUNC] kmem_cache_alloc(GFP_KERNEL)
fs/jffs2/malloc.c, 188: 
	kmem_cache_alloc in jffs2_alloc_refblock
fs/jffs2/malloc.c, 221: 
	jffs2_alloc_refblock in jffs2_prealloc_raw_node_refs
fs/jffs2/wbuf.c, 164: 
	jffs2_prealloc_raw_node_refs in jffs2_block_refile
fs/jffs2/wbuf.c, 927: 
	jffs2_block_refile in jffs2_flash_writev
fs/jffs2/wbuf.c, 924: 
	spin_lock in jffs2_flash_writev

To fix it, GFP_KERNEL in kmem_cache_alloc() is replaced with GFP_ATOMIC.
	
This is found by my static analysis tool (DSAC).

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 fs/jffs2/malloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jffs2/malloc.c b/fs/jffs2/malloc.c
index ce1189793288..66496ef09716 100644
--- a/fs/jffs2/malloc.c
+++ b/fs/jffs2/malloc.c
@@ -185,7 +185,7 @@ static struct jffs2_raw_node_ref *jffs2_alloc_refblock(void)
 {
 	struct jffs2_raw_node_ref *ret;
 
-	ret = kmem_cache_alloc(raw_node_ref_slab, GFP_KERNEL);
+	ret = kmem_cache_alloc(raw_node_ref_slab, GFP_ATOMIC);
 	if (ret) {
 		int i = 0;
 		for (i=0; i < REFS_PER_BLOCK; i++) {
-- 
2.17.0