Messages in this thread |  | | Date | Mon, 5 Dec 2022 09:55:43 +0800 | Subject | Re: [PATCH] erofs: Fix pcluster become inline when m_pa is zero | From | Chen Zhongjin <> |
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Hi,
On 2022/12/3 21:40, Gao Xiang wrote: > On Sat, Dec 03, 2022 at 09:20:17PM +0800, Gao Xiang wrote: >> 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 > Oh, I just realized my patch may be incorrect, I think we need to > just fail out this (since m_pblk == 0 cannot be a real pcluster, > since it has on-disk super block at least): > > diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c > index ab22100be861..e14e6c32e70d 100644 > --- a/fs/erofs/zdata.c > +++ b/fs/erofs/zdata.c > @@ -496,7 +496,8 @@ static int z_erofs_register_pcluster(struct > z_erofs_decompress_frontend *fe) > struct erofs_workgroup *grp; > int err; > > - if (!(map->m_flags & EROFS_MAP_ENCODED)) { > + if (!(map->m_flags & EROFS_MAP_ENCODED) || > + !(map->m_pa >> PAGE_SHIFT)) { > DBG_BUGON(1); > return -EFSCORRUPTED; > > > Could you resend next version behaving like the above? Thanks for your time and review!
I just didn't know weather m_pa is legal to be zero. I tested this and simply fail here can also solve the memleak.
Have sent v2 for this. And the title is slightly changed, see: [PATCH v2] erofs: Fix pcluster memleak when m_pa is zero
Best, Chen > Thanks, > Gao Xiang > >> 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 >>>
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