From 7b5843b702383a8523e512a837107d9e5a19d297 Mon Sep 17 00:00:00 2001 From: Gao Xiang Date: Tue, 31 Oct 2023 14:05:24 +0800 Subject: [PATCH] erofs: fix erofs_insert_workgroup() lockref usage [ Upstream commit 1a0ac8bd7a4fa5b2f4ef14c3b1e9d6e5a5faae06 ] As Linus pointed out [1], lockref_put_return() is fundamentally designed to be something that can fail. It behaves as a fastpath-only thing, and the failure case needs to be handled anyway. Actually, since the new pcluster was just allocated without being populated, it won't be accessed by others until it is inserted into XArray, so lockref helpers are actually unneeded here. Let's just set the proper reference count on initializing. [1] https://lore.kernel.org/r/CAHk-=whCga8BeQnJ3ZBh_Hfm9ctba_wpF444LpwRybVNMzO6Dw@mail.gmail.com Fixes: 7674a42f35ea ("erofs: use struct lockref to replace handcrafted approach") Reviewed-by: Chao Yu Link: https://lore.kernel.org/r/20231031060524.1103921-1-hsiangkao@linux.alibaba.com Signed-off-by: Gao Xiang Signed-off-by: Sasha Levin --- fs/erofs/utils.c | 8 +------- fs/erofs/zdata.c | 1 + 2 files changed, 2 insertions(+), 7 deletions(-) diff --git a/fs/erofs/utils.c b/fs/erofs/utils.c index cc6fb9e..4256a85 100644 --- a/fs/erofs/utils.c +++ b/fs/erofs/utils.c @@ -77,12 +77,7 @@ struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb, struct erofs_sb_info *const sbi = EROFS_SB(sb); struct erofs_workgroup *pre; - /* - * Bump up before making this visible to others for the XArray in order - * to avoid potential UAF without serialized by xa_lock. - */ - lockref_get(&grp->lockref); - + DBG_BUGON(grp->lockref.count < 1); repeat: xa_lock(&sbi->managed_pslots); pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index, @@ -96,7 +91,6 @@ repeat: cond_resched(); goto repeat; } - lockref_put_return(&grp->lockref); grp = pre; } xa_unlock(&sbi->managed_pslots); diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 036f610..a7e6847 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -796,6 +796,7 @@ static int z_erofs_register_pcluster(struct z_erofs_decompress_frontend *fe) return PTR_ERR(pcl); spin_lock_init(&pcl->obj.lockref.lock); + pcl->obj.lockref.count = 1; /* one ref for this request */ pcl->algorithmformat = map->m_algorithmformat; pcl->length = 0; pcl->partial = true; -- 2.7.4