lkml.org 
[lkml]   [2022]   [Dec]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] erofs: Fix pcluster become inline when m_pa is zero
Hi Zhongjin,

On Sat, Dec 03, 2022 at 05:45:27PM +0800, Chen Zhongjin wrote:
> syzkaller reported a memleak:
> https://syzkaller.appspot.com/bug?id=62f37ff612f0021641eda5b17f056f1668aa9aed
>
> unreferenced object 0xffff88811009c7f8 (size 136):
> ...
> backtrace:
> [<ffffffff821db19b>] z_erofs_do_read_page+0x99b/0x1740
> [<ffffffff821dee9e>] z_erofs_readahead+0x24e/0x580
> [<ffffffff814bc0d6>] read_pages+0x86/0x3d0
> ...
>
> syzkaller constructed a case: in z_erofs_register_pcluster(),
> ztailpacking = false and map->m_pa = zero. This makes pcl->obj.index
> become zero although pcl is not an inline pcluster.

Thanks for the patch!

We should just fail out if map->m_pa / EROFS_BLKSIZ == 0.

>
> Then following path adds refcount for grp, but the it won't be put
> because pcl is inline, which makes pcl not released when shrink.
>
> z_erofs_readahead()
> z_erofs_do_read_page() # for another page
> z_erofs_collector_begin()
> erofs_find_workgroup()
> erofs_workgroup_get()
>
> To fix this, add an attribute in z_erofs_pcluster to mark the inline
> state which not depends on index of grp.

I think the main reason is "inline pcluster _always_ did memory leak
before since I don't find any chance to these free inline pclusters
in the current codebase.

Actually I submitted a patch for this, could you check/review this
if possible?
https://lore.kernel.org/r/20221202033327.52702-1-hsiangkao@linux.alibaba.com

Thanks,
Gao Xiang

>
> Fixes: cecf864d3d76 ("erofs: support inline data decompression")
> Reported-by: syzbot+6f8cd9a0155b366d227f@syzkaller.appspotmail.com
> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
> ---
> fs/erofs/zdata.c | 2 +-
> fs/erofs/zdata.h | 5 ++++-
> 2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> index b792d424d774..fef2624d19e3 100644
> --- a/fs/erofs/zdata.c
> +++ b/fs/erofs/zdata.c
> @@ -517,7 +517,7 @@ static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe)
> DBG_BUGON(!mutex_trylock(&pcl->lock));
>
> if (ztailpacking) {
> - pcl->obj.index = 0; /* which indicates ztailpacking */
> + pcl->is_inline = true; /* which indicates ztailpacking */
> pcl->pageofs_in = erofs_blkoff(map->m_pa);
> pcl->tailpacking_size = map->m_plen;
> } else {
> diff --git a/fs/erofs/zdata.h b/fs/erofs/zdata.h
> index d98c95212985..35051ad27521 100644
> --- a/fs/erofs/zdata.h
> +++ b/fs/erofs/zdata.h
> @@ -78,6 +78,9 @@ struct z_erofs_pcluster {
> unsigned short tailpacking_size;
> };
>
> + /* I: whether it is inline or not */
> + bool is_inline;
> +
> /* I: compression algorithm format */
> unsigned char algorithmformat;
>
> @@ -115,7 +118,7 @@ struct z_erofs_decompressqueue {
>
> static inline bool z_erofs_is_inline_pcluster(struct z_erofs_pcluster *pcl)
> {
> - return !pcl->obj.index;
> + return pcl->is_inline;
> }
>
> static inline unsigned int z_erofs_pclusterpages(struct z_erofs_pcluster *pcl)
> --
> 2.17.1
>

\
 
 \ /
  Last update: 2022-12-03 14:21    [W:0.072 / U:0.208 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site