Chao Yu <c...@kernel.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 <c...@kernel.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 <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>
> >>>> ---
> >>>> 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
> >>
>
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