iwlwifi: mvm: writing zero bytes to debugfs causes a crash

commit 251fe09f13bfb54c1ede66ee8bf8ddd0061c4f7c upstream.

This is a static analysis fix.  The warning is:

	drivers/net/wireless/intel/iwlwifi/mvm/fw-dbg.c:912 iwl_mvm_fw_dbg_collect()
	warn: integer overflows 'sizeof(*desc) + len'

I guess this code is supposed to take a NUL character, but if we write
zero bytes then it tries to write -1 characters and crashes.

Fixes: c91b865cb14d ("iwlwifi: mvm: support description for user triggered fw dbg collection")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c b/drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c
index 7b7d2a146e30..0bda91ffc608 100644
--- a/drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/debugfs.c
@@ -1056,6 +1056,8 @@ static ssize_t iwl_dbgfs_fw_dbg_collect_write(struct iwl_mvm *mvm,
 
         if (ret)
                 return ret;
+        if (count == 0)
+                return 0;
 
         iwl_mvm_fw_dbg_collect(mvm, FW_DBG_TRIGGER_USER, buf,
                                (count - 1), NULL);