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| author | Greg Kurz <gkurz@linux.vnet.ibm.com> | 2014-10-31 07:50:11 +0100 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2014-11-19 18:38:15 +0100 |
| commit | 50e52368e667f2a8d5a43c0c9f60b4391a5bc715 (patch) | |
| tree | 5a9767bf5db43d8e5cef76851940aff44f6ecfc5 /drivers | |
| parent | e5fbc698350a42a56f5c165dbb6283d69b65d3f3 (diff) | |
| download | lwn-50e52368e667f2a8d5a43c0c9f60b4391a5bc715.tar.gz lwn-50e52368e667f2a8d5a43c0c9f60b4391a5bc715.zip | |
hwrng: pseries - port to new read API and fix stack corruption
commit 24c65bc7037e7d0f362c0df70d17dd72ee64b8b9 upstream.
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 d3cc7996473a7bdd33256029988ea690754e4e2a
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.
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/char/hw_random/pseries-rng.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/char/hw_random/pseries-rng.c b/drivers/char/hw_random/pseries-rng.c index b761459a3436..ab11c16352f8 100644 --- a/drivers/char/hw_random/pseries-rng.c +++ b/drivers/char/hw_random/pseries-rng.c @@ -26,18 +26,21 @@ #define MODULE_NAME "pseries-rng" -static int pseries_rng_data_read(struct hwrng *rng, u32 *data) +static int pseries_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) { + u64 buffer[PLPAR_HCALL_BUFSIZE]; + size_t size = max < 8 ? max : 8; int rc; - rc = plpar_hcall(H_RANDOM, (unsigned long *)data); + rc = plpar_hcall(H_RANDOM, (unsigned long *)buffer); if (rc != H_SUCCESS) { pr_err_ratelimited("H_RANDOM call failed %d\n", rc); return -EIO; } + memcpy(data, buffer, size); /* The hypervisor interface returns 64 bits */ - return 8; + return size; } /** @@ -56,7 +59,7 @@ static unsigned long pseries_rng_get_desired_dma(struct vio_dev *vdev) static struct hwrng pseries_rng = { .name = MODULE_NAME, - .data_read = pseries_rng_data_read, + .read = pseries_rng_read, }; static int __init pseries_rng_probe(struct vio_dev *dev, |