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Date: Wed, 14 Mar 2018 07:09:57 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: Larry Finger <Larry.Finger@...inger.net>
Cc: Kalle Valo <kvalo@...eaurora.org>, kernel-hardening@...ts.openwall.com,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-wireless@...r.kernel.org, Tycho Andersen <tycho@...ho.ws>,
Kees Cook <keescook@...omium.org>
Subject: Re: [RESEND PATCH] rsi: Remove stack VLA usage
On Sun, Mar 11, 2018 at 09:06:10PM -0500, Larry Finger wrote:
> On 03/11/2018 08:43 PM, Tobin C. Harding wrote:
> >The kernel would like to have all stack VLA usage removed[1]. rsi uses
> >a VLA based on 'blksize'. Elsewhere in the SDIO code maximum block size
> >is defined using a magic number. We can use a pre-processor defined
> >constant and declare the array to maximum size. We add a check before
> >accessing the array in case of programmer error.
> >
> >[1]: https://lkml.org/lkml/2018/3/7/621
> >
> >Signed-off-by: Tobin C. Harding <me@...in.cc>
> >---
> >
> >RESEND: add wireless mailing list to CC's (requested by Kalle)
> >
> > drivers/net/wireless/rsi/rsi_91x_hal.c | 13 +++++++------
> > drivers/net/wireless/rsi/rsi_91x_sdio.c | 9 +++++++--
> > 2 files changed, 14 insertions(+), 8 deletions(-)
> >
> >diff --git a/drivers/net/wireless/rsi/rsi_91x_hal.c b/drivers/net/wireless/rsi/rsi_91x_hal.c
> >index 1176de646942..839ebdd602df 100644
> >--- a/drivers/net/wireless/rsi/rsi_91x_hal.c
> >+++ b/drivers/net/wireless/rsi/rsi_91x_hal.c
> >@@ -641,7 +641,7 @@ static int ping_pong_write(struct rsi_hw *adapter, u8 cmd, u8 *addr, u32 size)
> > u32 cmd_addr;
> > u16 cmd_resp, cmd_req;
> > u8 *str;
> >- int status;
> >+ int status, ret;
> > if (cmd == PING_WRITE) {
> > cmd_addr = PING_BUFFER_ADDRESS;
> >@@ -655,12 +655,13 @@ static int ping_pong_write(struct rsi_hw *adapter, u8 cmd, u8 *addr, u32 size)
> > str = "PONG_VALID";
> > }
> >- status = hif_ops->load_data_master_write(adapter, cmd_addr, size,
> >+ ret = hif_ops->load_data_master_write(adapter, cmd_addr, size,
> > block_size, addr);
> >- if (status) {
> >- rsi_dbg(ERR_ZONE, "%s: Unable to write blk at addr %0x\n",
> >- __func__, *addr);
> >- return status;
> >+ if (ret) {
> >+ if (ret != -EINVAL)
> >+ rsi_dbg(ERR_ZONE, "%s: Unable to write blk at addr %0x\n",
> >+ __func__, *addr);
> >+ return ret;
> > }
> > status = bl_cmd(adapter, cmd_req, cmd_resp, str);
> >diff --git a/drivers/net/wireless/rsi/rsi_91x_sdio.c b/drivers/net/wireless/rsi/rsi_91x_sdio.c
> >index b0cf41195051..b766578b591a 100644
> >--- a/drivers/net/wireless/rsi/rsi_91x_sdio.c
> >+++ b/drivers/net/wireless/rsi/rsi_91x_sdio.c
> >@@ -20,6 +20,8 @@
> > #include "rsi_common.h"
> > #include "rsi_hal.h"
> >+#define RSI_MAX_BLOCK_SIZE 256
> >+
> > /**
> > * rsi_sdio_set_cmd52_arg() - This function prepares cmd 52 read/write arg.
> > * @rw: Read/write
> >@@ -362,7 +364,7 @@ static int rsi_setblocklength(struct rsi_hw *adapter, u32 length)
> > rsi_dbg(INIT_ZONE, "%s: Setting the block length\n", __func__);
> > status = sdio_set_block_size(dev->pfunction, length);
> >- dev->pfunction->max_blksize = 256;
> >+ dev->pfunction->max_blksize = RSI_MAX_BLOCK_SIZE;
> > adapter->block_size = dev->pfunction->max_blksize;
> > rsi_dbg(INFO_ZONE,
> >@@ -567,9 +569,12 @@ static int rsi_sdio_load_data_master_write(struct rsi_hw *adapter,
> > {
> > u32 num_blocks, offset, i;
> > u16 msb_address, lsb_address;
> >- u8 temp_buf[block_size];
> >+ u8 temp_buf[RSI_MAX_BLOCK_SIZE];
> > int status;
> >+ if (block_size > RSI_MAX_BLOCK_SIZE)
> >+ return -EINVAL;
> >+
> > num_blocks = instructions_sz / block_size;
> > msb_address = base_address >> 16;
>
> I am not giving this patch a negative review, but my solution to the same
> problem has been to change the on-stack array into a u8 pointer, use
> kmalloc() to assign the space, and then free that space at the end. That way
> large stack allocations are avoided, with a minimum of changes.
Your idea is better Larry, have you got a patch done already or do you
want me to knock one up?
thanks,
Tobin.
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