[PATCH v2 1/3] ocfs2: reject dinodes with non-canonical i_mode type

[Michael Bommarito <michael.bommarito@gmail.com>]

ocfs2_validate_inode_block() currently accepts any non-zero i_mode value.
ocfs2_populate_inode() then copies that mode verbatim into inode->i_mode
and dispatches on i_mode & S_IFMT to the file/dir/symlink/special_file
iops; an unrecognised type falls through to ocfs2_special_file_iops and
init_special_inode().

Reject dinodes whose type bits do not name one of the seven canonical
POSIX file types.  Use fs_umode_to_ftype(), the same generic file-type
conversion helper OCFS2 already uses for directory entries, so the
accepted inode type set matches the kernel file-type vocabulary instead
of open-coding a local switch.

Apply the same structural check to the online filecheck read path.
filecheck keeps its own error namespace, so it reports malformed i_mode
through the filecheck logger and OCFS2_FILECHECK_ERR_INVALIDINO instead
of calling ocfs2_error(), but it must not allow a malformed dinode to
proceed into ocfs2_populate_inode().

Fixes: b657c95c1108 ("ocfs2: Wrap inode block reads in a dedicated function.")
Cc: stable@vger.kernel.org
Link: https://sashiko.dev/#/patchset/20260517111015.3187935-1-michael.bommarito%40gmail.com
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Assisted-by: Claude:claude-opus-4-7
---
 fs/ocfs2/inode.c | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/inode.c b/fs/ocfs2/inode.c
index a510a0eb1adcc..e149ccbdc03ce 100644
--- a/fs/ocfs2/inode.c
+++ b/fs/ocfs2/inode.c
@@ -13,6 +13,7 @@
 #include <linux/pagemap.h>
 #include <linux/quotaops.h>
 #include <linux/iversion.h>
+#include <linux/fs_dirent.h>
 
 #include <asm/byteorder.h>
 
@@ -64,7 +65,12 @@ static int ocfs2_filecheck_read_inode_block_full(struct inode *inode,
 static int ocfs2_filecheck_validate_inode_block(struct super_block *sb,
 						struct buffer_head *bh);
 static int ocfs2_filecheck_repair_inode_block(struct super_block *sb,
-					      struct buffer_head *bh);
+						      struct buffer_head *bh);
+
+static bool ocfs2_valid_inode_mode(umode_t mode)
+{
+	return fs_umode_to_ftype(mode) != FT_UNKNOWN;
+}
 
 void ocfs2_set_inode_flags(struct inode *inode)
 {
@@ -1494,6 +1500,24 @@ int ocfs2_validate_inode_block(struct super_block *sb,
 		goto bail;
 	}
 
+	/*
+	 * Reject dinodes whose i_mode does not name one of the seven
+	 * canonical POSIX file types.  ocfs2_populate_inode() copies
+	 * i_mode verbatim into inode->i_mode and then dispatches via
+	 * switch (mode & S_IFMT) to file/dir/symlink/special_file iops;
+	 * an unrecognised type falls into ocfs2_special_file_iops with
+	 * init_special_inode(), which interprets i_rdev.  Constrain the
+	 * type here so the dispatch only ever sees a value mkfs.ocfs2 /
+	 * VFS can produce.
+	 */
+	if (!ocfs2_valid_inode_mode(le16_to_cpu(di->i_mode))) {
+		rc = ocfs2_error(sb,
+				 "Invalid dinode #%llu: mode 0%o has unknown file type\n",
+				 (unsigned long long)bh->b_blocknr,
+				 le16_to_cpu(di->i_mode));
+		goto bail;
+	}
+
 	if (le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL) {
 		struct ocfs2_inline_data *data = &di->id2.i_data;
 
@@ -1624,6 +1648,15 @@ static int ocfs2_filecheck_validate_inode_block(struct super_block *sb,
 		     (unsigned long long)bh->b_blocknr,
 		     le32_to_cpu(di->i_fs_generation));
 		rc = -OCFS2_FILECHECK_ERR_GENERATION;
+		goto bail;
+	}
+
+	if (!ocfs2_valid_inode_mode(le16_to_cpu(di->i_mode))) {
+		mlog(ML_ERROR,
+		     "Filecheck: invalid dinode #%llu: mode 0%o has unknown file type\n",
+		     (unsigned long long)bh->b_blocknr,
+		     le16_to_cpu(di->i_mode));
+		rc = -OCFS2_FILECHECK_ERR_INVALIDINO;
 	}
 
 bail:
@@ -1812,4 +1845,3 @@ const struct ocfs2_caching_operations ocfs2_inode_caching_ops = {
 	.co_io_lock		= ocfs2_inode_cache_io_lock,
 	.co_io_unlock		= ocfs2_inode_cache_io_unlock,
 };
-
-- 
2.53.0