hwrng: pseries - port to new read API and fix stack corruption
The add_early_randomness() function in drivers/char/hw_random/core.c passes
a 16-byte buffer to pseries_rng_data_read(). Unfortunately, plpar_hcall()
returns four 64-bit values and trashes 16 bytes on the stack.
This bug has been lying around for a long time. It got unveiled by:
commit d3cc799647
Author: Amit Shah <amit.shah@redhat.com>
Date: Thu Jul 10 15:42:34 2014 +0530
hwrng: fetch randomness only after device init
It may trig a oops while loading or unloading the pseries-rng module for both
PowerVM and PowerKVM guests.
This patch does two things:
- pass an intermediate well sized buffer to plpar_hcall(). This is acceptalbe
since we're not on a hot path.
- move to the new read API so that we know the return buffer size for sure.
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
parent
738459e3f8
commit
24c65bc703
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@ -25,18 +25,21 @@
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#include <asm/vio.h>
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static int pseries_rng_data_read(struct hwrng *rng, u32 *data)
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static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
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{
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u64 buffer[PLPAR_HCALL_BUFSIZE];
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size_t size = max < 8 ? max : 8;
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int rc;
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rc = plpar_hcall(H_RANDOM, (unsigned long *)data);
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rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer);
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if (rc != H_SUCCESS) {
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pr_err_ratelimited("H_RANDOM call failed %d\n", rc);
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return -EIO;
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}
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memcpy(data, buffer, size);
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/* The hypervisor interface returns 64 bits */
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return 8;
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return size;
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}
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/**
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@ -55,7 +58,7 @@ static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev)
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static struct hwrng pseries_rng = {
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.name = KBUILD_MODNAME,
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.data_read = pseries_rng_data_read,
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.read = pseries_rng_read,
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};
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static int __init pseries_rng_probe(struct vio_dev *dev,
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