From: Greg Kurz Date: Fri, 31 Oct 2014 06:50:11 +0000 (+0100) Subject: hwrng: pseries - port to new read API and fix stack corruption X-Git-Tag: v3.12.34~82 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=50e52368e667f2a8d5a43c0c9f60b4391a5bc715;p=thirdparty%2Fkernel%2Fstable.git 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 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 Signed-off-by: Herbert Xu Signed-off-by: Jiri Slaby --- diff --git a/drivers/char/hw_random/pseries-rng.c b/drivers/char/hw_random/pseries-rng.c index b761459a3436c..ab11c16352f82 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,