Patch "net/rds: fix possible cp null dereference" has been added to the 4.19-stable tree

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This is a note to let you know that I've just added the patch titled

    net/rds: fix possible cp null dereference

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-rds-fix-possible-cp-null-dereference.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 62fc3357e079a07a22465b9b6ef71bb6ea75ee4b Mon Sep 17 00:00:00 2001
From: Mahmoud Adam <mngyadam@xxxxxxxxxx>
Date: Tue, 26 Mar 2024 16:31:33 +0100
Subject: net/rds: fix possible cp null dereference

From: Mahmoud Adam <mngyadam@xxxxxxxxxx>

commit 62fc3357e079a07a22465b9b6ef71bb6ea75ee4b upstream.

cp might be null, calling cp->cp_conn would produce null dereference

[Simon Horman adds:]

Analysis:

* cp is a parameter of __rds_rdma_map and is not reassigned.

* The following call-sites pass a NULL cp argument to __rds_rdma_map()

  - rds_get_mr()
  - rds_get_mr_for_dest

* Prior to the code above, the following assumes that cp may be NULL
  (which is indicative, but could itself be unnecessary)

	trans_private = rs->rs_transport->get_mr(
		sg, nents, rs, &mr->r_key, cp ? cp->cp_conn : NULL,
		args->vec.addr, args->vec.bytes,
		need_odp ? ODP_ZEROBASED : ODP_NOT_NEEDED);

* The code modified by this patch is guarded by IS_ERR(trans_private),
  where trans_private is assigned as per the previous point in this analysis.

  The only implementation of get_mr that I could locate is rds_ib_get_mr()
  which can return an ERR_PTR if the conn (4th) argument is NULL.

* ret is set to PTR_ERR(trans_private).
  rds_ib_get_mr can return ERR_PTR(-ENODEV) if the conn (4th) argument is NULL.
  Thus ret may be -ENODEV in which case the code in question will execute.

Conclusion:
* cp may be NULL at the point where this patch adds a check;
  this patch does seem to address a possible bug

Fixes: c055fc00c07b ("net/rds: fix WARNING in rds_conn_connect_if_down")
Cc: stable@xxxxxxxxxxxxxxx # v4.19+
Signed-off-by: Mahmoud Adam <mngyadam@xxxxxxxxxx>
Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240326153132.55580-1-mngyadam@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/rds/rdma.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -279,7 +279,7 @@ static int __rds_rdma_map(struct rds_soc
 		kfree(sg);
 		ret = PTR_ERR(trans_private);
 		/* Trigger connection so that its ready for the next retry */
-		if (ret == -ENODEV)
+		if (ret == -ENODEV && cp)
 			rds_conn_connect_if_down(cp->cp_conn);
 		goto out;
 	}


Patches currently in stable-queue which might be from mngyadam@xxxxxxxxxx are

queue-4.19/net-rds-fix-possible-cp-null-dereference.patch




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