[PATCH AUTOSEL 6.13 2/8] ntb: reduce stack usage in idt_scan_mws

Sasha Levin
2025-04-07T18:17:06Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit aff12700b8dd7422bfe2277696e192af4df9de8f ]

idt_scan_mws() puts a large fixed-size array on the stack and copies
it into a smaller dynamically allocated array at the end. On 32-bit
targets, the fixed size can easily exceed the warning limit for
possible stack overflow:

drivers/ntb/hw/idt/ntb_hw_idt.c:1041:27: error: stack frame size (1032) exceeds limit (1024) in 'idt_scan_mws' [-Werror,-Wframe-larger-than]

Change it to instead just always use dynamic allocation for the
array from the start. It's too big for the stack, but not actually
all that much for a permanent allocation.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/all/202205111109.PiKTruEj-lkp@intel.com/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/ntb/hw/idt/ntb_hw_idt.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/drivers/ntb/hw/idt/ntb_hw_idt.c b/drivers/ntb/hw/idt/ntb_hw_idt.c
index 544d8a4d2af59..f27df8d7f3b97 100644
--- a/drivers/ntb/hw/idt/ntb_hw_idt.c
+++ b/drivers/ntb/hw/idt/ntb_hw_idt.c
@@ -1041,7 +1041,7 @@ static inline char *idt_get_mw_name(enum idt_mw_type mw_type)
static struct idt_mw_cfg *idt_scan_mws(struct idt_ntb_dev *ndev, int port,
unsigned char *mw_cnt)
{
- struct idt_mw_cfg mws[IDT_MAX_NR_MWS], *ret_mws;
+ struct idt_mw_cfg *mws;
const struct idt_ntb_bar *bars;
enum idt_mw_type mw_type;
unsigned char widx, bidx, en_cnt;
@@ -1049,6 +1049,11 @@ static struct idt_mw_cfg *idt_scan_mws(struct idt_ntb_dev *ndev, int port,
int aprt_size;
u32 data;

+ mws = devm_kcalloc(&ndev->ntb.pdev->dev, IDT_MAX_NR_MWS,
+ sizeof(*mws), GFP_KERNEL);
+ if (!mws)
+ return ERR_PTR(-ENOMEM);
+
/* Retrieve the array of the BARs registers */
bars = portdata_tbl[port].bars;

@@ -1103,16 +1108,7 @@ static struct idt_mw_cfg *idt_scan_mws(struct idt_ntb_dev *ndev, int port,
}
}

- /* Allocate memory for memory window descriptors */
- ret_mws = devm_kcalloc(&ndev->ntb.pdev->dev, *mw_cnt, sizeof(*ret_mws),
- GFP_KERNEL);
- if (!ret_mws)
- return ERR_PTR(-ENOMEM);
-
- /* Copy the info of detected memory windows */
- memcpy(ret_mws, mws, (*mw_cnt)*sizeof(*ret_mws));
-
- return ret_mws;
+ return mws;
}

/*
--
2.39.5