[PATCH linux-next] SUNRPC: rpcrdma_register_default_external: Dynamically allocate ib_phys_buf

[Tim Gardner]

rpcrdma_register_default_external() is several frames into
the call stack which goes deeper yet. You run the risk of stack
corruption by declaring such a large automatic variable,
so dynamically allocate the array of 'struct ib_phys_buf' objects in
order to silence the frame-larger-than warning.

net/sunrpc/xprtrdma/verbs.c: In function 'rpcrdma_register_default_external':
net/sunrpc/xprtrdma/verbs.c:1774:1: warning: the frame size of 1056 bytes is larger than 1024 bytes [-Wframe-larger-than=]

gcc version 4.6.3

Cc: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Tom Tucker <tom@xxxxxx>
Cc: Haggai Eran <haggaie@xxxxxxxxxxxx>
Cc: Or Gerlitz <ogerlitz@xxxxxxxxxxxx>
Cc: Shani Michaeli <shanim@xxxxxxxxxxxx>
Cc: linux-nfs@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
---
 net/sunrpc/xprtrdma/verbs.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 93726560..0916467 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1736,9 +1736,13 @@ rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg,
 	int mem_priv = (writing ? IB_ACCESS_REMOTE_WRITE :
 				  IB_ACCESS_REMOTE_READ);
 	struct rpcrdma_mr_seg *seg1 = seg;
-	struct ib_phys_buf ipb[RPCRDMA_MAX_DATA_SEGS];
+	struct ib_phys_buf *ipb;
 	int len, i, rc = 0;
 
+	ipb = kmalloc(sizeof(*ipb) * RPCRDMA_MAX_DATA_SEGS, GFP_KERNEL);
+	if (!ipb)
+		return -ENOMEM;
+
 	if (*nsegs > RPCRDMA_MAX_DATA_SEGS)
 		*nsegs = RPCRDMA_MAX_DATA_SEGS;
 	for (len = 0, i = 0; i < *nsegs;) {
@@ -1770,6 +1774,7 @@ rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg,
 		seg1->mr_len = len;
 	}
 	*nsegs = i;
+	kfree(ipb);
 	return rc;
 }
 
-- 
1.7.9.5

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