[PATCH v4 6/7] smb: client: fix file type corruption in posix_reparse_to_fattr()

[Paulo Alcantara <pc@manguebit.org>]

Setting the file type in cf_mode without clearing the existing S_IFMT
bits first is wrong as it corrupts the file type when cf_mode already
has type bits set (e.g. S_IFREG | S_IFCHR == S_IFLNK).

Use a local ftype variable to collect the new file type and apply it
after validation succeeds, clearing S_IFMT and setting the new type in
a single assignment.  This avoids stripping cf_mode on malformed
reparse points where the function returns false early.

Closes: https://sashiko.dev/#/patchset/20260906172005.627163-1-pc%40manguebit.org
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/reparse.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 8a19dee564b8..616ca2dbfac4 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -1212,6 +1212,7 @@ static bool posix_reparse_to_fattr(struct cifs_sb_info *cifs_sb,
 				   struct cifs_open_info_data *data)
 {
 	struct reparse_nfs_data_buffer *buf = (struct reparse_nfs_data_buffer *)data->reparse.buf;
+	umode_t ftype;
 
 	if (buf == NULL)
 		return true;
@@ -1227,7 +1228,7 @@ static bool posix_reparse_to_fattr(struct cifs_sb_info *cifs_sb,
 			WARN_ON_ONCE(1);
 			return false;
 		}
-		fattr->cf_mode |= S_IFCHR;
+		ftype = S_IFCHR;
 		fattr->cf_rdev = reparse_mkdev(buf->DataBuffer);
 		break;
 	case NFS_SPECFILE_BLK:
@@ -1235,22 +1236,23 @@ static bool posix_reparse_to_fattr(struct cifs_sb_info *cifs_sb,
 			WARN_ON_ONCE(1);
 			return false;
 		}
-		fattr->cf_mode |= S_IFBLK;
+		ftype = S_IFBLK;
 		fattr->cf_rdev = reparse_mkdev(buf->DataBuffer);
 		break;
 	case NFS_SPECFILE_FIFO:
-		fattr->cf_mode |= S_IFIFO;
+		ftype = S_IFIFO;
 		break;
 	case NFS_SPECFILE_SOCK:
-		fattr->cf_mode |= S_IFSOCK;
+		ftype = S_IFSOCK;
 		break;
 	case NFS_SPECFILE_LNK:
-		fattr->cf_mode |= S_IFLNK;
+		ftype = S_IFLNK;
 		break;
 	default:
 		WARN_ON_ONCE(1);
 		return false;
 	}
+	fattr->cf_mode = (fattr->cf_mode & ~S_IFMT) | ftype;
 	return true;
 }
 
-- 
2.55.0