Commit 9a7d5a9e authored by Aurelien Aptel's avatar Aurelien Aptel Committed by Steve French
Browse files

cifs: fix possible uninitialized access and race on iface_list 



iface[0] was accessed regardless of the count value and without
locking.

* check count before accessing any ifaces
* make copy of iface list (it's a simple POD array) and use it without
  locking.

Signed-off-by: default avatarAurelien Aptel <aaptel@suse.com>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
Reviewed-by: default avatarPaulo Alcantara (SUSE) <pc@cjr.nz>
parent 3345bb44

fs/cifs/sess.c

+26 −3
Original line number Diff line number Diff line
@@ -77,6 +77,8 @@ int cifs_try_adding_channels(struct cifs_ses *ses) 
	int i = 0;

	int rc = 0;

	int tries = 0;

	struct cifs_server_iface *ifaces = NULL;

	size_t iface_count;



	if (left <= 0) {

		cifs_dbg(FYI,
@@ -90,6 +92,26 @@ int cifs_try_adding_channels(struct cifs_ses *ses) 
		return 0;

	}



	/*

	 * Make a copy of the iface list at the time and use that

	 * instead so as to not hold the iface spinlock for opening

	 * channels

	 */

	spin_lock(&ses->iface_lock);

	iface_count = ses->iface_count;

	if (iface_count <= 0) {

		spin_unlock(&ses->iface_lock);

		cifs_dbg(FYI, "no iface list available to open channels\n");

		return 0;

	}

	ifaces = kmemdup(ses->iface_list, iface_count*sizeof(*ifaces),

			 GFP_ATOMIC);

	if (!ifaces) {

		spin_unlock(&ses->iface_lock);

		return 0;

	}

	spin_unlock(&ses->iface_lock);



	/*

	 * Keep connecting to same, fastest, iface for all channels as

	 * long as its RSS. Try next fastest one if not RSS or channel
@@ -105,9 +127,9 @@ int cifs_try_adding_channels(struct cifs_ses *ses) 
			break;

		}



		iface = &ses->iface_list[i];

		iface = &ifaces[i];

		if (is_ses_using_iface(ses, iface) && !iface->rss_capable) {

			i = (i+1) % ses->iface_count;

			i = (i+1) % iface_count;

			continue;

		}
@@ -115,7 +137,7 @@ int cifs_try_adding_channels(struct cifs_ses *ses) 
		if (rc) {

			cifs_dbg(FYI, "failed to open extra channel on iface#%d rc=%d\n",

				 i, rc);

			i = (i+1) % ses->iface_count;

			i = (i+1) % iface_count;

			continue;

		}
@@ -124,6 +146,7 @@ int cifs_try_adding_channels(struct cifs_ses *ses) 
		left--;

	}



	kfree(ifaces);

	return ses->chan_count - old_chan_count;

}