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Subject[PATCH v2 3/5] f2fs: fix to avoid NULL pointer dereference
Date
Unable to handle kernel NULL pointer dereference at virtual address 00000000
PC is at f2fs_free_dic+0x60/0x2c8
LR is at f2fs_decompress_pages+0x3c4/0x3e8
f2fs_free_dic+0x60/0x2c8
f2fs_decompress_pages+0x3c4/0x3e8
__read_end_io+0x78/0x19c
f2fs_post_read_work+0x6c/0x94
process_one_work+0x210/0x48c
worker_thread+0x2e8/0x44c
kthread+0x110/0x120
ret_from_fork+0x10/0x18

In f2fs_free_dic(), we can not use f2fs_put_page(,1) to release dic->tpages[i],
as the page's mapping is NULL.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
v2:
- fix to skip release tpages[i] if it is NULL in error path.
fs/f2fs/compress.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index ef7dd04312fe..6e10800729b6 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -1137,7 +1137,10 @@ void f2fs_free_dic(struct decompress_io_ctx *dic)
for (i = 0; i < dic->cluster_size; i++) {
if (dic->rpages[i])
continue;
- f2fs_put_page(dic->tpages[i], 1);
+ if (!dic->tpages[i])
+ continue;
+ unlock_page(dic->tpages[i]);
+ put_page(dic->tpages[i]);
}
kfree(dic->tpages);
}
--
2.18.0.rc1
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