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?"
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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