6.5-stable review patch. If anyone has any objections, please let me know.
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From: Gao Xiang hsiangkao@linux.alibaba.com
[ 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_wpF444LpwRybVNMzO6D...
Fixes: 7674a42f35ea ("erofs: use struct lockref to replace handcrafted approach") Reviewed-by: Chao Yu chao@kernel.org Link: https://lore.kernel.org/r/20231031060524.1103921-1-hsiangkao@linux.alibaba.c... Signed-off-by: Gao Xiang hsiangkao@linux.alibaba.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 cc6fb9e988991..4256a85719a1d 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 @@ struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb, 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 9bfdb4ad7c763..2461a3f74e744 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -805,6 +805,7 @@ 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;