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mmc: pwrseq: Use kmalloc_array instead of stack VLA
[ Upstream commit 486e666136
]
The use of stack Variable Length Arrays needs to be avoided, as they
can be a vector for stack exhaustion, which can be both a runtime bug
(kernel Oops) or a security flaw (overwriting memory beyond the
stack). Also, in general, as code evolves it is easy to lose track of
how big a VLA can get. Thus, we can end up having runtime failures
that are hard to debug. As part of the directive[1] to remove all VLAs
from the kernel, and build with -Wvla.
Currently driver is using a VLA declared using the number of descriptors. This
array is used to store integer values and is later used as an argument to
`gpiod_set_array_value_cansleep()` This can be avoided by using
`kmalloc_array()` to allocate memory for the array of integer values. Memory is
free'd before return from function.
>From the code it appears that it is safe to sleep so we can use GFP_KERNEL
(based _cansleep() suffix of function `gpiod_set_array_value_cansleep()`.
It can be expected that this patch will result in a small increase in overhead
due to the use of `kmalloc_array()`
[1] https://lkml.org/lkml/2018/3/7/621
Signed-off-by: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 9 additions and 5 deletions
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@ -39,14 +39,18 @@ static void mmc_pwrseq_simple_set_gpios_value(struct mmc_pwrseq_simple *pwrseq,
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struct gpio_descs *reset_gpios = pwrseq->reset_gpios;
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if (!IS_ERR(reset_gpios)) {
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int i;
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int values[reset_gpios->ndescs];
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int i, *values;
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int nvalues = reset_gpios->ndescs;
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for (i = 0; i < reset_gpios->ndescs; i++)
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values = kmalloc_array(nvalues, sizeof(int), GFP_KERNEL);
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if (!values)
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return;
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for (i = 0; i < nvalues; i++)
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values[i] = value;
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gpiod_set_array_value_cansleep(
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reset_gpios->ndescs, reset_gpios->desc, values);
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gpiod_set_array_value_cansleep(nvalues, reset_gpios->desc, values);
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kfree(values);
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}
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}
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