linux-kernel - [PATCH] [v2] scsi: mpi3mr: reduce stack usage in mpi3mr_refresh_sas

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Date: Tue, 23 Jan 2024 14:07:36 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Sathya Prakash Veerichetty <sathya.prakash@...adcom.com>,
	Kashyap Desai <kashyap.desai@...adcom.com>,
	Sumit Saxena <sumit.saxena@...adcom.com>,
	Sreekanth Reddy <sreekanth.reddy@...adcom.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Johannes Thumshirn <johannes.thumshirn@....com>,
	"James E.J. Bottomley" <jejb@...ux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Ranjan Kumar <ranjan.kumar@...adcom.com>,
	Tomas Henzl <thenzl@...hat.com>,
	Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
	mpi3mr-linuxdrv.pdl@...adcom.com,
	linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] [v2] scsi: mpi3mr: reduce stack usage in mpi3mr_refresh_sas_ports()

From: Arnd Bergmann <arnd@...db.de>

Doubling the number of PHYs also doubled the stack usage of this function,
exceeding the 32-bit limit of 1024 bytes:

drivers/scsi/mpi3mr/mpi3mr_transport.c: In function 'mpi3mr_refresh_sas_ports':
drivers/scsi/mpi3mr/mpi3mr_transport.c:1818:1: error: the frame size of 1636 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

Since the sas_io_unit_pg0 structure is already allocated dynamically, use
the same method here. The size of the allocation can be smaller based on the
actual number of phys now, so use this as an upper bound.

Fixes: cb5b60894602 ("scsi: mpi3mr: Increase maximum number of PHYs to 64 from 32")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@....com>
Cc: Sathya Prakash Veerichetty <sathya.prakash@...adcom.com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
v2: fix number of ports to be always 64 rather than num_phys
---
 drivers/scsi/mpi3mr/mpi3mr_transport.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/scsi/mpi3mr/mpi3mr_transport.c b/drivers/scsi/mpi3mr/mpi3mr_transport.c
index c0c8ab586957..d32ad46318cb 100644
--- a/drivers/scsi/mpi3mr/mpi3mr_transport.c
+++ b/drivers/scsi/mpi3mr/mpi3mr_transport.c
@@ -1671,7 +1671,7 @@ mpi3mr_update_mr_sas_port(struct mpi3mr_ioc *mrioc, struct host_port *h_port,
 void
 mpi3mr_refresh_sas_ports(struct mpi3mr_ioc *mrioc)
 {
-	struct host_port h_port[64];
+	struct host_port *h_port = NULL;
 	int i, j, found, host_port_count = 0, port_idx;
 	u16 sz, attached_handle, ioc_status;
 	struct mpi3_sas_io_unit_page0 *sas_io_unit_pg0 = NULL;
@@ -1685,6 +1685,10 @@ mpi3mr_refresh_sas_ports(struct mpi3mr_ioc *mrioc)
 	sas_io_unit_pg0 = kzalloc(sz, GFP_KERNEL);
 	if (!sas_io_unit_pg0)
 		return;
+	h_port = kcalloc(64, sizeof(struct host_port), GFP_KERNEL);
+	if (!h_port)
+		goto out;
+
 	if (mpi3mr_cfg_get_sas_io_unit_pg0(mrioc, sas_io_unit_pg0, sz)) {
 		ioc_err(mrioc, "failure at %s:%d/%s()!\n",
 		    __FILE__, __LINE__, __func__);
@@ -1814,6 +1818,7 @@ mpi3mr_refresh_sas_ports(struct mpi3mr_ioc *mrioc)
 		}
 	}
 out:
+	kfree(h_port);
 	kfree(sas_io_unit_pg0);
 }
 
-- 
2.39.2