[PATCH 6.12 1096/1102] ocfs2: validate dx_root extent list fields during block read

6.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joseph Qi <joseph.qi@linux.alibaba.com>

[ Upstream commit 775c17386a6fd695f999d4cda90e3931386570dd ]

Patch series "ocfs2: consolidate extent list validation into block read
callbacks".

ocfs2 validates extent list fields (l_count, l_next_free_rec) at various
points during extent tree traversal.  This is fragile because each caller
must remember to check for corrupted on-disk data before using it.

This series moves those checks into the block read validation callbacks
(ocfs2_validate_dx_root and ocfs2_validate_extent_block), so corrupted
fields are caught early at block read time.  Redundant post-read checks
are then removed.

This patch (of 4):

Move the extent list l_count validation from ocfs2_dx_dir_lookup_rec()
into ocfs2_validate_dx_root(), so that corrupted on-disk fields are caught
early at block read time rather than during directory lookups.

Additionally, add a l_next_free_rec <= l_count check to prevent
out-of-bounds access when iterating over extent records.

Both checks are skipped for inline dx roots (OCFS2_DX_FLAG_INLINE), which
use dr_entries instead of dr_list.

Link: https://lkml.kernel.org/r/20260403090803.3860971-1-joseph.qi@linux.alibaba.com
Link: https://lkml.kernel.org/r/20260403090803.3860971-2-joseph.qi@linux.alibaba.com
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: Heming Zhao <heming.zhao@suse.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <redacted>
Cc: Changwei Ge <redacted>
Cc: Jun Piao <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stable-dep-of: bc70726ddad5 ("ocfs2: validate directory-index entry counts when reading metadata")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/ocfs2/dir.c |   26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

--- a/fs/ocfs2/dir.c
+++ b/fs/ocfs2/dir.c

@@ -580,7 +580,7 @@ static int ocfs2_validate_dx_root(struct
 		mlog(ML_ERROR,
 		     "Checksum failed for dir index root block %llu\n",
 		     (unsigned long long)bh->b_blocknr);
-		return ret;
+		goto bail;
 	}
 
 	if (!OCFS2_IS_VALID_DX_ROOT(dx_root)) {

@@ -588,8 +588,32 @@ static int ocfs2_validate_dx_root(struct
 				  "Dir Index Root # %llu has bad signature %.*s\n",
 				  (unsigned long long)le64_to_cpu(dx_root->dr_blkno),
 				  7, dx_root->dr_signature);
+		goto bail;
 	}
 
+	if (!(dx_root->dr_flags & OCFS2_DX_FLAG_INLINE)) {
+		struct ocfs2_extent_list *el = &dx_root->dr_list;
+
+		if (le16_to_cpu(el->l_count) != ocfs2_extent_recs_per_dx_root(sb)) {
+			ret = ocfs2_error(sb,
+					  "Dir Index Root # %llu has invalid l_count %u (expected %u)\n",
+					  (unsigned long long)le64_to_cpu(dx_root->dr_blkno),
+					  le16_to_cpu(el->l_count),
+					  ocfs2_extent_recs_per_dx_root(sb));
+			goto bail;
+		}
+
+		if (le16_to_cpu(el->l_next_free_rec) > le16_to_cpu(el->l_count)) {
+			ret = ocfs2_error(sb,
+					  "Dir Index Root # %llu has invalid l_next_free_rec %u (l_count %u)\n",
+					  (unsigned long long)le64_to_cpu(dx_root->dr_blkno),
+					  le16_to_cpu(el->l_next_free_rec),
+					  le16_to_cpu(el->l_count));
+			goto bail;
+		}
+	}
+
+bail:
 	return ret;
 }