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Message-ID: <20241024075203.ifih3rxwyzl7dn4s@skbuf>
Date: Thu, 24 Oct 2024 10:52:03 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Frank Li <Frank.Li@....com>
Cc: Mark Brown <broonie@...nel.org>,
William Zhang <william.zhang@...adcom.com>,
Heiko Stuebner <heiko@...ech.de>,
Cédric Le Goater <clg@...d.org>,
Dhruva Gole <d-gole@...com>,
Amit Kumar Mahapatra <amit.kumar-mahapatra@....com>,
"open list:FREESCALE DSPI DRIVER" <linux-spi@...r.kernel.org>,
"open list:FREESCALE DSPI DRIVER" <imx@...ts.linux.dev>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] spi: spi-fsl-dspi: Fix crash when not using GPIO
chip select
Hi Frank,
On Wed, Oct 23, 2024 at 04:30:32PM -0400, Frank Li wrote:
> Add check for the return value of spi_get_csgpiod() to avoid passing a NULL
> pointer to gpiod_direction_output(), preventing a crash when GPIO chip
> select is not used.
>
> Fix below crash:
> [ 4.251960] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> [ 4.260762] Mem abort info:
> [ 4.263556] ESR = 0x0000000096000004
> [ 4.267308] EC = 0x25: DABT (current EL), IL = 32 bits
> [ 4.272624] SET = 0, FnV = 0
> [ 4.275681] EA = 0, S1PTW = 0
> [ 4.278822] FSC = 0x04: level 0 translation fault
> [ 4.283704] Data abort info:
> [ 4.286583] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
> [ 4.292074] CM = 0, WnR = 0, TnD = 0, TagAccess = 0
> [ 4.297130] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
> [ 4.302445] [0000000000000000] user address but active_mm is swapper
> [ 4.308805] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
> [ 4.315072] Modules linked in:
> [ 4.318124] CPU: 2 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12.0-rc4-next-20241023-00008-ga20ec42c5fc1 #359
> [ 4.328130] Hardware name: LS1046A QDS Board (DT)
> [ 4.332832] pstate: 40000005 (nZcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 4.339794] pc : gpiod_direction_output+0x34/0x5c
> [ 4.344505] lr : gpiod_direction_output+0x18/0x5c
> [ 4.349208] sp : ffff80008003b8f0
> [ 4.352517] x29: ffff80008003b8f0 x28: 0000000000000000 x27: ffffc96bcc7e9068
> [ 4.359659] x26: ffffc96bcc6e00b0 x25: ffffc96bcc598398 x24: ffff447400132810
> [ 4.366800] x23: 0000000000000000 x22: 0000000011e1a300 x21: 0000000000020002
> [ 4.373940] x20: 0000000000000000 x19: 0000000000000000 x18: ffffffffffffffff
> [ 4.381081] x17: ffff44740016e600 x16: 0000000500000003 x15: 0000000000000007
> [ 4.388221] x14: 0000000000989680 x13: 0000000000020000 x12: 000000000000001e
> [ 4.395362] x11: 0044b82fa09b5a53 x10: 0000000000000019 x9 : 0000000000000008
> [ 4.402502] x8 : 0000000000000002 x7 : 0000000000000007 x6 : 0000000000000000
> [ 4.409641] x5 : 0000000000000200 x4 : 0000000002000000 x3 : 0000000000000000
> [ 4.416781] x2 : 0000000000022202 x1 : 0000000000000000 x0 : 0000000000000000
> [ 4.423921] Call trace:
> [ 4.426362] gpiod_direction_output+0x34/0x5c (P)
> [ 4.431067] gpiod_direction_output+0x18/0x5c (L)
> [ 4.435771] dspi_setup+0x220/0x334
>
> Fixes: 9e264f3f85a5 ("spi: Replace all spi->chip_select and spi->cs_gpiod references with function call")
> Cc: stable@...r.kernel.org
> Signed-off-by: Frank Li <Frank.Li@....com>
> ---
Sadly I do not reproduce this NULL pointer dereference. I also know from
hearsay that the GPIO consumer API is more or less NULL-tolerant. Could
you "make drivers/gpio/gpiolib.lst" and see what's at offsets 0x18 and
0x34 into gpiod_direction_output()? The first thing in that function is
the VALIDATE_DESC() macro, which does:
static int validate_desc(const struct gpio_desc *desc, const char *func)
{
if (!desc)
return 0;
if (IS_ERR(desc)) {
pr_warn("%s: invalid GPIO (errorpointer)\n", func);
return PTR_ERR(desc);
}
return 1;
}
#define VALIDATE_DESC(desc) do { \
int __valid = validate_desc(desc, __func__); \
if (__valid <= 0) \
return __valid; \
} while (0)
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