cifs: clean up the SecurityFlags write handler

The SecurityFlags handler uses an obsolete simple_strtoul() call, and
doesn't really handle the bounds checking well. Fix it to use
kstrtouint() instead. Clean up the error messages as well and fix a
bogus check for an unsigned int to be less than 0.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <smfrench@gmail.com>

1 files changed, 14 insertions, 6 deletions

diff --git a/fs/cifs/cifs_debug.c b/fs/cifs/cifs_debug.c
index d59748346020..856f8f5fc295 100644
--- a/fs/cifs/cifs_debug.c
+++ b/fs/cifs/cifs_debug.c
@@ -598,6 +598,7 @@ static int cifs_security_flags_proc_open(struct inode *inode, struct file *file)
 static ssize_t cifs_security_flags_proc_write(struct file *file,
                 const char __user *buffer, size_t count, loff_t *ppos)
 {
+        int rc;
         unsigned int flags;
         char flags_string[12];
         char c;
@@ -620,26 +621,33 @@ static ssize_t cifs_security_flags_proc_write(struct file *file,
                         global_secflags = CIFSSEC_MAX;
                         return count;
                 } else if (!isdigit(c)) {
-                        cifs_dbg(VFS, "invalid flag %c\n", c);
+                        cifs_dbg(VFS, "Invalid SecurityFlags: %s\n",
+                                        flags_string);
                         return -EINVAL;
                 }
         }
-        /* else we have a number */
 
-        flags = simple_strtoul(flags_string, NULL, 0);
+        /* else we have a number */
+        rc = kstrtouint(flags_string, 0, &flags);
+        if (rc) {
+                cifs_dbg(VFS, "Invalid SecurityFlags: %s\n",
+                                flags_string);
+                return rc;
+        }
 
         cifs_dbg(FYI, "sec flags 0x%x\n", flags);
 
-        if (flags <= 0)  {
-                cifs_dbg(VFS, "invalid security flags %s\n", flags_string);
+        if (flags == 0)  {
+                cifs_dbg(VFS, "Invalid SecurityFlags: %s\n", flags_string);
                 return -EINVAL;
         }
 
         if (flags & ~CIFSSEC_MASK) {
-                cifs_dbg(VFS, "attempt to set unsupported security flags 0x%x\n",
+                cifs_dbg(VFS, "Unsupported security flags: 0x%x\n",
                          flags & ~CIFSSEC_MASK);
                 return -EINVAL;
         }
+
         /* flags look ok - update the global security flags for cifs module */
         global_secflags = flags;
         if (global_secflags & CIFSSEC_MUST_SIGN) {