fs/f2fs/compress.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
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 __iget before f2fs_free_dic and iput after free the dic.
Cc: Daeho Jeong <daehojeong@google.com>
Fixes: bff139b49d9f ("f2fs: handle decompress only post processing in softirq")
Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
Signed-off-by: Baocong Liu <baocong.liu@unisoc.com>
---
v2: use __iget/iput function
---
fs/f2fs/compress.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index b3c1df9..3f0c18d 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 +1785,20 @@ 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);
+ __iget(dic->inode);
+ spin_unlock(&dic->inode->i_lock);
queue_work(F2FS_I_SB(dic->inode)->post_read_wq,
&dic->free_work);
}
--
1.9.1On 6/4/25 19:37, 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 __iget before f2fs_free_dic and iput after free the dic.
>
> Cc: Daeho Jeong <daehojeong@google.com>
> Fixes: bff139b49d9f ("f2fs: handle decompress only post processing in softirq")
> Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
> Signed-off-by: Baocong Liu <baocong.liu@unisoc.com>
> ---
> v2: use __iget/iput function
> ---
> fs/f2fs/compress.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> index b3c1df9..3f0c18d 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 +1785,20 @@ 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);
> + __iget(dic->inode);
> + spin_unlock(&dic->inode->i_lock);
Oh, how about using igrab() instead?
> queue_work(F2FS_I_SB(dic->inode)->post_read_wq,
> &dic->free_work);
> }
Chao Yu <chao@kernel.org> 于2025年6月5日周四 10:23写道：
>
> On 6/4/25 19:37, 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 __iget before f2fs_free_dic and iput after free the dic.
> >
> > Cc: Daeho Jeong <daehojeong@google.com>
> > Fixes: bff139b49d9f ("f2fs: handle decompress only post processing in softirq")
> > Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
> > Signed-off-by: Baocong Liu <baocong.liu@unisoc.com>
> > ---
> > v2: use __iget/iput function
> > ---
> > fs/f2fs/compress.c | 16 +++++++++++-----
> > 1 file changed, 11 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> > index b3c1df9..3f0c18d 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 +1785,20 @@ 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);
> > + __iget(dic->inode);
> > + spin_unlock(&dic->inode->i_lock);
>
> Oh, how about using igrab() instead?
Hi Chao,
after I check igrab, I think it is ok,
but here We don't need care about igarb's return value, right?
Thanks!
>
> > queue_work(F2FS_I_SB(dic->inode)->post_read_wq,
> > &dic->free_work);
> > }
>
On 6/5/25 10:44, Zhiguo Niu wrote:
> Chao Yu <chao@kernel.org> 于2025年6月5日周四 10:23写道：
>>
>> On 6/4/25 19:37, 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 __iget before f2fs_free_dic and iput after free the dic.
>>>
>>> Cc: Daeho Jeong <daehojeong@google.com>
>>> Fixes: bff139b49d9f ("f2fs: handle decompress only post processing in softirq")
>>> Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
>>> Signed-off-by: Baocong Liu <baocong.liu@unisoc.com>
>>> ---
>>> v2: use __iget/iput function
>>> ---
>>> fs/f2fs/compress.c | 16 +++++++++++-----
>>> 1 file changed, 11 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
>>> index b3c1df9..3f0c18d 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 +1785,20 @@ 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);
>>> + __iget(dic->inode);
>>> + spin_unlock(&dic->inode->i_lock);
>>
>> Oh, how about using igrab() instead?
> Hi Chao,
> after I check igrab, I think it is ok,
> but here We don't need care about igarb's return value, right?
I guess "return NULL" should be impossible case, but still we can add
f2fs_bug_on() to detect any potential bug, right?
Thanks,
> Thanks!
>
>>
>>> queue_work(F2FS_I_SB(dic->inode)->post_read_wq,
>>> &dic->free_work);
>>> }
>>
Chao Yu <chao@kernel.org> 于2025年6月5日周四 11:31写道：
>
> On 6/5/25 10:44, Zhiguo Niu wrote:
> > Chao Yu <chao@kernel.org> 于2025年6月5日周四 10:23写道：
> >>
> >> On 6/4/25 19:37, 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 __iget before f2fs_free_dic and iput after free the dic.
> >>>
> >>> Cc: Daeho Jeong <daehojeong@google.com>
> >>> Fixes: bff139b49d9f ("f2fs: handle decompress only post processing in softirq")
> >>> Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
> >>> Signed-off-by: Baocong Liu <baocong.liu@unisoc.com>
> >>> ---
> >>> v2: use __iget/iput function
> >>> ---
> >>> fs/f2fs/compress.c | 16 +++++++++++-----
> >>> 1 file changed, 11 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
> >>> index b3c1df9..3f0c18d 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 +1785,20 @@ 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);
> >>> + __iget(dic->inode);
> >>> + spin_unlock(&dic->inode->i_lock);
> >>
> >> Oh, how about using igrab() instead?
> > Hi Chao,
> > after I check igrab, I think it is ok,
> > but here We don't need care about igarb's return value, right?
>
> I guess "return NULL" should be impossible case, but still we can add
> f2fs_bug_on() to detect any potential bug, right?
OK, thanks for your suggestions.
>
> Thanks,
>
> > Thanks!
> >
> >>
> >>> queue_work(F2FS_I_SB(dic->inode)->post_read_wq,
> >>> &dic->free_work);
> >>> }
> >>
>
© 2016 - 2025 Red Hat, Inc.