[v2] cifs: fix possible uninitialized access and race on iface_list
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Message ID 20191204151454.29253-1-aaptel@suse.com
State New
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Series
  • [v2] cifs: fix possible uninitialized access and race on iface_list
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Commit Message

Aurélien Aptel Dec. 4, 2019, 3:14 p.m. UTC
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: Aurelien Aptel <aaptel@suse.com>
---
changes since v1:
* remove unecessary kfree()

 fs/cifs/sess.c | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

Comments

Steve French Dec. 4, 2019, 5:55 p.m. UTC | #1
tentatively merged into cifs-2.6.git for-next and buildbot github tree
pending testing

On Wed, Dec 4, 2019 at 9:59 AM Paulo Alcantara <pc@cjr.nz> wrote:
>
> Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
>
> On December 4, 2019 12:14:54 PM GMT-03:00, Aurelien Aptel <aaptel@suse.com> wrote:
>>
>> 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: Aurelien Aptel <aaptel@suse.com>
>> ________________________________
>> changes since v1:
>> * remove unecessary kfree()
>>
>>  fs/cifs/sess.c | 29 ++++++++++++++++++++++++++---
>>  1 file changed, 26 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
>> index fb3bdc44775c..396400cf2800 100644
>> --- a/fs/cifs/sess.c
>> +++ b/fs/cifs/sess.c
>> @@ -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;
>>  }
>>
>
>
> --
> Sent from my p≡p for Android.

Patch
diff mbox series

diff --git a/fs/cifs/sess.c b/fs/cifs/sess.c
index fb3bdc44775c..396400cf2800 100644
--- a/fs/cifs/sess.c
+++ b/fs/cifs/sess.c
@@ -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;
 }