[PATCH v7.3 3/9] cifs: Fix validation of EAs for WSL reparse points

[Pali Rohár]

When wsl_to_fattr() is called from readdir() then we should skip validation
of WSL EAs because readdir FIND_FIRST/NEXT results do not provide EA values
at all. For readdir() reply in this case return DT_UNKNOWN type instead of
DT_REG (which is the result of failed WSL EAs validation).

When validation is skipped and some required EAs are missing then returns
true from wsl_to_fattr() function but do not set fattr->cf_mode. This makes
readdir() to return DT_UNKNOWN type in the same way as it is doing NFS
reparse point function.

This change fixes readdir() result that for some WSL reparse points returns
DT_REG due to missing EAs. After this change it returns DT_UNKNOWN, which
is better than returning wrong type.

Fixes: ef201e8759d2 ("cifs: Validate EAs for WSL reparse points")
Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
---
 fs/smb/client/reparse.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/fs/smb/client/reparse.c b/fs/smb/client/reparse.c
index 3a27773186ae..e547510ca3c5 100644
--- a/fs/smb/client/reparse.c
+++ b/fs/smb/client/reparse.c
@@ -1152,6 +1152,7 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 	kuid_t uid = cifs_sb->ctx->linux_uid;
 	kgid_t gid = cifs_sb->ctx->linux_gid;
 	struct smb2_file_full_ea_info *ea;
+	bool ignore_missing_eas = false;
 	bool have_xattr_dev = false;
 	dev_t rdev = 0;
 	umode_t mode;
@@ -1174,8 +1175,18 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 	case IO_REPARSE_TAG_LX_BLK:
 		mode |= S_IFBLK;
 		break;
+	default:
+		return false;
 	}
 
+	/*
+	 * When reparse buffer is not available then this is from readdir() call
+	 * which does not provide EAs. readdir() can return DT_UNKNOWN type,
+	 * which is signaled by no filling the fattr->cf_mode and returning true.
+	 */
+	if (!data->reparse.buf && !data->wsl.eas_len)
+		ignore_missing_eas = true;
+
 	if (!data->wsl.eas_len)
 		goto out;
 
@@ -1213,7 +1224,7 @@ static bool wsl_to_fattr(struct cifs_open_info_data *data,
 out:
 	/* Major and minor numbers for char and block devices are mandatory. */
 	if (!have_xattr_dev && (tag == IO_REPARSE_TAG_LX_CHR || tag == IO_REPARSE_TAG_LX_BLK))
-		return false;
+		return ignore_missing_eas;
 
 	fattr->cf_uid = uid;
 	fattr->cf_gid = gid;
-- 
2.20.1