The decompress_io_ctx may be released asynchronously after
I/O completion. If this file is deleted immediately after read,
and the kworker of processing post_read_wq has not been executed yet
due to high workloads, It is possible that the inode(f2fs_inode_info)
is evicted and freed before it is used f2fs_free_dic.
The UAF case as below:
Thread A Thread B
- f2fs_decompress_end_io
- f2fs_put_dic
- queue_work
add free_dic work to post_read_wq
- do_unlink
- iput
- evict
- call_rcu
This file is deleted after read.
Thread C kworker to process post_read_wq
- rcu_do_batch
- f2fs_free_inode
- kmem_cache_free
inode is freed by rcu
- process_scheduled_works
- f2fs_late_free_dic
- f2fs_free_dic
- f2fs_release_decomp_mem
read (dic->inode)->i_compress_algorithm
This patch increase inode->i_count before f2fs_free_dic and decrease it
after free the dic.
Cc: Daeho Jeong <daehoje...@google.com>
Fixes: bff139b49d9f ("f2fs: handle decompress only post processing in softirq")
Signed-off-by: Zhiguo Niu <zhiguo....@unisoc.com>
Signed-off-by: Baocong Liu <baocong....@unisoc.com>
---
fs/f2fs/compress.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index b3c1df9..6b3b3a7 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -1687,7 +1687,7 @@ static void f2fs_release_decomp_mem(struct
decompress_io_ctx *dic,
}
static void f2fs_free_dic(struct decompress_io_ctx *dic,
- bool bypass_destroy_callback);
+ bool bypass_destroy_callback, bool late_free);
struct decompress_io_ctx *f2fs_alloc_dic(struct compress_ctx *cc)
{
@@ -1743,12 +1743,12 @@ struct decompress_io_ctx *f2fs_alloc_dic(struct
compress_ctx *cc)
return dic;
out_free:
- f2fs_free_dic(dic, true);
+ f2fs_free_dic(dic, true, false);
return ERR_PTR(ret);
}
static void f2fs_free_dic(struct decompress_io_ctx *dic,
- bool bypass_destroy_callback)
+ bool bypass_destroy_callback, bool late_free)
{
int i;
@@ -1775,6 +1775,11 @@ static void f2fs_free_dic(struct decompress_io_ctx *dic,
}
page_array_free(dic->inode, dic->rpages, dic->nr_rpages);
+ if (late_free) {
+ spin_lock(&dic->inode->i_lock);
+ atomic_dec(&dic->inode->i_count);
+ spin_unlock(&dic->inode->i_lock);
+ }
kmem_cache_free(dic_entry_slab, dic);
}
@@ -1783,16 +1788,20 @@ static void f2fs_late_free_dic(struct work_struct *work)
struct decompress_io_ctx *dic =
container_of(work, struct decompress_io_ctx, free_work);
- f2fs_free_dic(dic, false);
+ f2fs_free_dic(dic, false, true);
}
static void f2fs_put_dic(struct decompress_io_ctx *dic, bool in_task)
{
if (refcount_dec_and_test(&dic->refcnt)) {
if (in_task) {
- f2fs_free_dic(dic, false);
+ f2fs_free_dic(dic, false, false);
} else {
INIT_WORK(&dic->free_work, f2fs_late_free_dic);
+ /* to avoid inode is evicted simultaneously */
+ spin_lock(&dic->inode->i_lock);
+ atomic_inc(&dic->inode->i_count);
+ spin_unlock(&dic->inode->i_lock);
queue_work(F2FS_I_SB(dic->inode)->post_read_wq,
&dic->free_work);
}
--
1.9.1
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