linux-kernel - [PATCH] fs: jffs2: fix possible sleep-in-atomic-context bugs

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Date:   Tue, 17 Dec 2019 21:51:43 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     dwmw2@...radead.org, richard@....at
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] fs: jffs2: fix possible sleep-in-atomic-context bugs

The filesystem may sleep while holding a spinlock.
The function call path (from bottom to top) in Linux 4.19 is:

fs/jffs2/malloc.c, 188: 
	kmem_cache_alloc(GFP_KERNEL) 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, 291: 
	jffs2_block_refile in jffs2_wbuf_recover
fs/jffs2/wbuf.c, 287: 
	spin_lock in jffs2_wbuf_recover

fs/jffs2/malloc.c, 188: 
    kmem_cache_alloc(GFP_KERNEL) 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

kmem_cache_alloc(GFP_KERNEL) can sleep at runtime.

To fix these possible bugs, GFP_KERNEL is replaced with GFP_ATOMIC for
kmem_cache_alloc().

These bugs are found by a static analysis tool STCheck written by myself.

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++) {
-- 
2.17.1