From 9a40c050f58344615a0604701b5d299519833163 Mon Sep 17 00:00:00 2001 From: Joseph Qi Date: Sat, 24 Oct 2026 23:10:08 +0800 Subject: [PATCH] ocfs2: find the xattr entry again after defragmenting a bucket ocfs2_xattr_set_entry_bucket() hands loc.xl_entry to ocfs2_xa_set() twice: once for the bucket as it stands, and, if that reports -ENOSPC, once more after ocfs2_defrag_xattr_bucket() has packed the name/value pairs down. Defragmenting ends by sorting the entry array on xe_name_hash. Buckets are kept sorted, so the sort only permutes entries that share a hash, but lib/sort.c is an unstable heapsort and it does permute them. loc.xl_entry is an address inside xh_entries[], so afterwards it denotes whichever entry landed in that slot rather than the one the search found. The second ocfs2_xa_set() then works on the wrong entry. Nothing on that path compares the entry's name with xi->xi_name, so what happens depends on how the two entries compare in size: ocfs2_xa_reuse_entry() trips its BUG_ON() when the padded name sizes differ, and otherwise the new value is written into the neighbouring attribute's value slot while the attribute being set is left untouched. setxattr() reports success either way. Remember the entry's hash before defragmenting and look the entry up again afterwards, the way ocfs2_xattr_bucket_find() does. An entry that cannot be found again means the bucket no longer holds what the search found, so fail with -EFSCORRUPTED rather than writing through the stale pointer. Link: https://lore.kernel.org/20261024151012.1059683-3-joseph.qi@linux.alibaba.com Fixes: 012255961c9e ("ocfs2: Enable xattr set in index btree") Signed-off-by: Joseph Qi Signed-off-by: Andrew Morton Cc: Heming Zhao Cc: Mark Fasheh Cc: Joel Becker Cc: --- fs/ocfs2/xattr.c | 30 +++++++++++++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c index bb5b12924e1b..d6d07116ce97 100644 --- a/fs/ocfs2/xattr.c +++ b/fs/ocfs2/xattr.c @@ -6052,13 +6052,18 @@ static int ocfs2_xattr_set_entry_bucket(struct inode *inode, struct ocfs2_xattr_search *xs, struct ocfs2_xattr_set_ctxt *ctxt) { - int ret; + int ret, found = 0; + u16 xe_index; + u32 name_hash; struct ocfs2_xa_loc loc; trace_ocfs2_xattr_set_entry_bucket(xi->xi_name); ocfs2_init_xattr_bucket_xa_loc(&loc, xs->bucket, xs->not_found ? NULL : xs->here); + /* Defragmenting below may move this entry, so remember its hash. */ + name_hash = loc.xl_entry ? le32_to_cpu(loc.xl_entry->xe_name_hash) : 0; + ret = ocfs2_xa_set(&loc, xi, ctxt); if (!ret) { xs->here = loc.xl_entry; @@ -6077,6 +6082,29 @@ static int ocfs2_xattr_set_entry_bucket(struct inode *inode, goto out; } + /* + * ocfs2_defrag_xattr_bucket() sorts the entries by name hash and + * lib/sort.c is not stable, so entries sharing a hash may have traded + * slots. Look the entry up again before writing through it. + */ + if (loc.xl_entry) { + ret = ocfs2_find_xe_in_bucket(inode, xs->bucket, + xi->xi_name_index, xi->xi_name, + name_hash, &xe_index, &found); + if (ret) { + mlog_errno(ret); + goto out; + } + if (!found) { + mlog(ML_ERROR, "xattr entry not found in bucket %llu after defrag\n", + (unsigned long long)bucket_blkno(xs->bucket)); + ret = -EFSCORRUPTED; + goto out; + } + loc.xl_entry = &bucket_xh(xs->bucket)->xh_entries[xe_index]; + xs->here = loc.xl_entry; + } + ret = ocfs2_xa_set(&loc, xi, ctxt); if (!ret) { xs->here = loc.xl_entry;