[PATCH 04/12] cifs: Fix and improve cifs_is_path_accessible() function

["Pali Rohár" <pali@kernel.org>]

Do not call SMBQueryInformation() command for path with SMB wildcard
characters on non-UNICODE connection because server expands wildcards.
Function cifs_is_path_accessible() needs to check if the real path exists
and must not expand wildcard characters.

Do not dynamically allocate memory for small FILE_ALL_INFO structure and
instead allocate it on the stack. This structure is allocated on stack by
all other functions.

When CAP_NT_SMBS was not negotiated then do not issue CIFSSMBQPathInfo()
command. This command returns failure by non-NT Win9x SMB servers, so there
is no need try it. The purpose of cifs_is_path_accessible() function is
just to check if the path is accessible, so SMBQueryInformation() for old
servers is enough.

Signed-off-by: Pali Rohár <pali@kernel.org>
---
 fs/smb/client/smb1ops.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/fs/smb/client/smb1ops.c b/fs/smb/client/smb1ops.c
index d959097ec2d2..bef8e03edf1d 100644
--- a/fs/smb/client/smb1ops.c
+++ b/fs/smb/client/smb1ops.c
@@ -520,21 +520,27 @@ static int
 cifs_is_path_accessible(const unsigned int xid, struct cifs_tcon *tcon,
 			struct cifs_sb_info *cifs_sb, const char *full_path)
 {
-	int rc;
-	FILE_ALL_INFO *file_info;
+	int rc = -EOPNOTSUPP;
+	FILE_ALL_INFO file_info;
 
-	file_info = kmalloc(sizeof(FILE_ALL_INFO), GFP_KERNEL);
-	if (file_info == NULL)
-		return -ENOMEM;
+	if (tcon->ses->capabilities & CAP_NT_SMBS)
+		rc = CIFSSMBQPathInfo(xid, tcon, full_path, &file_info,
+				      0 /* not legacy */, cifs_sb->local_nls,
+				      cifs_remap(cifs_sb));
 
-	rc = CIFSSMBQPathInfo(xid, tcon, full_path, file_info,
-			      0 /* not legacy */, cifs_sb->local_nls,
-			      cifs_remap(cifs_sb));
+	/*
+	 * Non-UNICODE variant of fallback functions below expands wildcards,
+	 * so they cannot be used for querying paths with wildcard characters.
+	 * Therefore for such paths returns -ENOENT as they cannot exist.
+	 */
+	if ((rc == -EOPNOTSUPP || rc == -EINVAL) &&
+	    !(tcon->ses->capabilities & CAP_UNICODE) &&
+	    strpbrk(full_path, "*?\"><"))
+		rc = -ENOENT;
 
 	if (rc == -EOPNOTSUPP || rc == -EINVAL)
-		rc = SMBQueryInformation(xid, tcon, full_path, file_info,
+		rc = SMBQueryInformation(xid, tcon, full_path, &file_info,
 				cifs_sb->local_nls, cifs_remap(cifs_sb));
-	kfree(file_info);
 	return rc;
 }
 
-- 
2.20.1