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Message-ID: <CAHJ8P3Lah5o60wJTb-H6Dng6sSrs8gY9cuFyw_1zAOAGfZMd_Q@mail.gmail.com>
Date: Wed, 11 Jun 2025 15:51:19 +0800
From: Zhiguo Niu <niuzhiguo84@...il.com>
To: Chao Yu <chao@...nel.org>
Cc: Jaegeuk Kim <jaegeuk@...nel.org>, Zhiguo Niu <zhiguo.niu@...soc.com>,
linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
ke.wang@...soc.com, Hao_hao.Wang@...soc.com, baocong.liu@...soc.com
Subject: Re: [PATCH v3] f2fs: compress: fix UAF of f2fs_inode_info in f2fs_free_dic
Zhiguo Niu <niuzhiguo84@...il.com> 于2025年6月11日周三 14:52写道：
>
> Chao Yu <chao@...nel.org> 于2025年6月11日周三 14:47写道：
> >
> > On 6/11/25 14:41, Zhiguo Niu wrote:
> > > Chao Yu <chao@...nel.org> 于2025年6月11日周三 14:07写道：
> > >>
> > >> On 6/11/25 00:08, Jaegeuk Kim wrote:
> > >>> Hi Zhiguo,
> > >>>
> > >>> This patch causes CPU hang when running fsstress on compressed/non-compressed
> > >>> files. Please check.
> > >>
> > >> Oh, seems it may cause below deadlock:
> > >>
> > >> CPU0
> > >> process A
> > >> - spin_lock(i_lock)
> > >> software IRQ
> > >> - end_io
> > >> - igrab
> > >> - spin_lock(i_lock)
> > >>
> > >> Thanks,
> > > Hi Chao,
> > > Thanks for pointing this out.
> > > I have tested this patch locally about some basic cases before submission.
> > > So it seems that should use the following method to solve this problem?
> > > " store i_compress_algorithm/sbi in dic to avoid inode access?"
> >
> > Zhiguo,
> >
> > Yeah, I guess so.
> Hi Chao,
> OK, I will prepare it .
> Thanks a lot.
> >
> > Thanks,
> >
> > > thanks！
> > >
> > >
> > >>
> > >>>
> > >>> On 06/05, Zhiguo Niu wrote:
> > >>>> 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 use igrab before f2fs_free_dic and iput after free the dic when dic free
> > >>>> action is done by kworker.
> > >>>>
> > >>>> Cc: Daeho Jeong <daehojeong@...gle.com>
> > >>>> Fixes: bff139b49d9f ("f2fs: handle decompress only post processing in softirq")
> > >>>> Signed-off-by: Zhiguo Niu <zhiguo.niu@...soc.com>
> > >>>> Signed-off-by: Baocong Liu <baocong.liu@...soc.com>
> > >>>> ---
> > >>>> v3: use igrab to replace __iget
> > >>>> v2: use __iget/iput function
> > >>>> ---
> > >>>> fs/f2fs/compress.c | 14 +++++++++-----
> > >>>> 1 file changed, 9 insertions(+), 5 deletions(-)
> > >>>>
> > >>>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > >>>> index b3c1df9..729ad16 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 +1775,8 @@ static void f2fs_free_dic(struct decompress_io_ctx *dic,
> > >>>> }
> > >>>>
> > >>>> page_array_free(dic->inode, dic->rpages, dic->nr_rpages);
> > >>>> + if (late_free)
> > >>>> + iput(dic->inode);
> > >>>> kmem_cache_free(dic_entry_slab, dic);
> > >>>> }
> > >>>>
> > >>>> @@ -1783,16 +1785,18 @@ 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);
> > >>>> + /* use igrab to avoid inode is evicted simultaneously */
> > >>>> + f2fs_bug_on(F2FS_I_SB(dic->inode), !igrab(dic->inode));
> > >>>> queue_work(F2FS_I_SB(dic->inode)->post_read_wq,
> > >>>> &dic->free_work);
> > >>>> }
> > >>>> --
> > >>>> 1.9.1
> > >>
> >
Hi Chao,
The patch is about as follows, because dic->sbi is used directly in
f2fs_free_dic: page_array_free(dic->sbi, dic->tpages, dic->cluster_size);
so there are two points I want to confirm:
1. As a corresponding, the first parameter (inode) of page_array_alloc
is need to modify to sbi or not ?
2. As a corresponding, do we need to add the sbi field in compress_ctx
so that page_array_alloc/free called
in compress flow can use sbi directly?
Thanks!
diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index b3c1df9..897d8ae 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -34,9 +34,8 @@ static void *page_array_alloc(struct inode *inode, int nr)
return f2fs_kzalloc(sbi, size, GFP_NOFS);
}
-static void page_array_free(struct inode *inode, void *pages, int nr)
+static void page_array_free(struct f2fs_sb_info *sbi, void *pages, int nr)
{
- struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
unsigned int size = sizeof(struct page *) * nr;
if (!pages)
@@ -155,7 +154,7 @@ int f2fs_init_compress_ctx(struct compress_ctx *cc)
void f2fs_destroy_compress_ctx(struct compress_ctx *cc, bool reuse)
{
- page_array_free(cc->inode, cc->rpages, cc->cluster_size);
+ page_array_free(F2FS_I_SB(cc->inode), cc->rpages, cc->cluster_size);
cc->rpages = NULL;
cc->nr_rpages = 0;
cc->nr_cpages = 0;
@@ -716,7 +715,7 @@ static int f2fs_compress_pages(struct compress_ctx *cc)
if (cc->cpages[i])
f2fs_compress_free_page(cc->cpages[i]);
}
- page_array_free(cc->inode, cc->cpages, cc->nr_cpages);
+ page_array_free(F2FS_I_SB(cc->inode), cc->cpages, cc->nr_cpages);
cc->cpages = NULL;
destroy_compress_ctx:
if (cops->destroy_compress_ctx)
@@ -734,7 +733,7 @@ static void f2fs_release_decomp_mem(struct
decompress_io_ctx *dic,
void f2fs_decompress_cluster(struct decompress_io_ctx *dic, bool in_task)
{
- struct f2fs_sb_info *sbi = F2FS_I_SB(dic->inode);
+ struct f2fs_sb_info *sbi = dic->sbi;
struct f2fs_inode_info *fi = F2FS_I(dic->inode);
const struct f2fs_compress_ops *cops =
f2fs_cops[fi->i_compress_algorithm];
@@ -1442,13 +1441,13 @@ static int f2fs_write_compressed_pages(struct
compress_ctx *cc,
spin_unlock(&fi->i_size_lock);
f2fs_put_rpages(cc);
- page_array_free(cc->inode, cc->cpages, cc->nr_cpages);
+ page_array_free(F2FS_I_SB(cc->inode), cc->cpages, cc->nr_cpages);
cc->cpages = NULL;
f2fs_destroy_compress_ctx(cc, false);
return 0;
out_destroy_crypt:
- page_array_free(cc->inode, cic->rpages, cc->cluster_size);
+ page_array_free(F2FS_I_SB(cc->inode), cic->rpages, cc->cluster_size);
for (--i; i >= 0; i--) {
if (!cc->cpages[i])
@@ -1469,7 +1468,7 @@ static int f2fs_write_compressed_pages(struct
compress_ctx *cc,
f2fs_compress_free_page(cc->cpages[i]);
cc->cpages[i] = NULL;
}
- page_array_free(cc->inode, cc->cpages, cc->nr_cpages);
+ page_array_free(F2FS_I_SB(cc->inode), cc->cpages, cc->nr_cpages);
cc->cpages = NULL;
return -EAGAIN;
}
@@ -1499,7 +1498,7 @@ void f2fs_compress_write_end_io(struct bio *bio,
struct page *page)
end_page_writeback(cic->rpages[i]);
}
- page_array_free(cic->inode, cic->rpages, cic->nr_rpages);
+ page_array_free(F2FS_I_SB(cic->inode), cic->rpages, cic->nr_rpages);
kmem_cache_free(cic_entry_slab, cic);
}
@@ -1637,7 +1636,7 @@ static int f2fs_prepare_decomp_mem(struct
decompress_io_ctx *dic,
f2fs_cops[F2FS_I(dic->inode)->i_compress_algorithm];
int i;
- if (!allow_memalloc_for_decomp(F2FS_I_SB(dic->inode), pre_alloc))
+ if (!allow_memalloc_for_decomp(dic->sbi, pre_alloc))
return 0;
dic->tpages = page_array_alloc(dic->inode, dic->cluster_size);
@@ -1670,10 +1669,9 @@ static int f2fs_prepare_decomp_mem(struct
decompress_io_ctx *dic,
static void f2fs_release_decomp_mem(struct decompress_io_ctx *dic,
bool bypass_destroy_callback, bool pre_alloc)
{
- const struct f2fs_compress_ops *cops =
- f2fs_cops[F2FS_I(dic->inode)->i_compress_algorithm];
+ const struct f2fs_compress_ops *cops =
f2fs_cops[dic->compress_algorithm];
- if (!allow_memalloc_for_decomp(F2FS_I_SB(dic->inode), pre_alloc))
+ if (!allow_memalloc_for_decomp(dic->sbi, pre_alloc))
return;
if (!bypass_destroy_callback && cops->destroy_decompress_ctx)
@@ -1708,6 +1706,8 @@ struct decompress_io_ctx *f2fs_alloc_dic(struct
compress_ctx *cc)
dic->magic = F2FS_COMPRESSED_PAGE_MAGIC;
dic->inode = cc->inode;
+ dic->sbi = sbi;
+ dic->compress_algorithm = F2FS_I(cc->inode)->i_compress_algorithm;
atomic_set(&dic->remaining_pages, cc->nr_cpages);
dic->cluster_idx = cc->cluster_idx;
dic->cluster_size = cc->cluster_size;
@@ -1762,7 +1762,7 @@ static void f2fs_free_dic(struct decompress_io_ctx *dic,
continue;
f2fs_compress_free_page(dic->tpages[i]);
}
- page_array_free(dic->inode, dic->tpages, dic->cluster_size);
+ page_array_free(dic->sbi, dic->tpages, dic->cluster_size);
}
if (dic->cpages) {
@@ -1771,10 +1771,10 @@ static void f2fs_free_dic(struct decompress_io_ctx *dic,
continue;
f2fs_compress_free_page(dic->cpages[i]);
}
- page_array_free(dic->inode, dic->cpages, dic->nr_cpages);
+ page_array_free(dic->sbi, dic->cpages, dic->nr_cpages);
}
- page_array_free(dic->inode, dic->rpages, dic->nr_rpages);
+ page_array_free(dic->sbi, dic->rpages, dic->nr_rpages);
kmem_cache_free(dic_entry_slab, dic);
}
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 9333a22b..da2137e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1536,6 +1536,7 @@ struct compress_io_ctx {
struct decompress_io_ctx {
u32 magic; /* magic number to indicate
page is compressed */
struct inode *inode; /* inode the context belong to */
+ struct f2fs_sb_info *sbi; /* f2fs_sb_info pointer */
pgoff_t cluster_idx; /* cluster index number */
unsigned int cluster_size; /* page count in cluster */
unsigned int log_cluster_size; /* log of cluster size */
@@ -1576,6 +1577,7 @@ struct decompress_io_ctx {
bool failed; /* IO error occurred before
decompression? */
bool need_verity; /* need fs-verity verification
after decompression? */
+ unsigned char compress_algorithm; /* backup algorithm type */
void *private; /* payload buffer for
specified decompression algorithm */
void *private2; /* extra payload buffer */
struct work_struct verity_work; /* work to verify the
decompressed pages */
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