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[PATCH 4.4 32/38] hwrng: core - Dont use a stack buffer in add_early_randomness()

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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Lutomirski <luto@kernel.org>

commit 6d4952d9d9d4dc2bb9c0255d95a09405a1e958f7 upstream.

hw_random carefully avoids using a stack buffer except in
add_early_randomness().  This causes a crash in virtio_rng if
CONFIG_VMAP_STACK=y.

Reported-by: Matt Mullins <mmullins@mmlx.us>
Tested-by: Matt Mullins <mmullins@mmlx.us>
Fixes: d3cc7996473a ("hwrng: fetch randomness only after device init")
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/char/hw_random/core.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/char/hw_random/core.c
+++ b/drivers/char/hw_random/core.c
@@ -84,14 +84,14 @@ static size_t rng_buffer_size(void)
 
 static void add_early_randomness(struct hwrng *rng)
 {
-	unsigned char bytes[16];
 	int bytes_read;
+	size_t size = min_t(size_t, 16, rng_buffer_size());
 
 	mutex_lock(&reading_mutex);
-	bytes_read = rng_get_data(rng, bytes, sizeof(bytes), 1);
+	bytes_read = rng_get_data(rng, rng_buffer, size, 1);
 	mutex_unlock(&reading_mutex);
 	if (bytes_read > 0)
-		add_device_randomness(bytes, bytes_read);
+		add_device_randomness(rng_buffer, bytes_read);
 }
 
 static inline void cleanup_rng(struct kref *kref)

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[PATCH 4.4 00/38] 4.4.33-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:40 +0100
  [PATCH 4.4 10/38] pinctrl: cherryview: Prevent possible interrupt storm on resume Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 06/38] coredump: fix unfreezable coredumping task Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 30/38] mei: bus: fix received data size check in NFC fixup Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 05/38] swapfile: fix memory corruption via malformed swapfile Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 33/38] i40e: fix call of ndo_dflt_bridge_getlink() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 11/38] staging: iio: ad5933: avoid uninitialized variable in error case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 29/38] iommu/vt-d: Fix dead-locks in disable_dmar_iommu() path Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 18/38] toshiba-wmi: Fix loading the driver on non Toshiba laptops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 28/38] iommu/amd: Free domain id when free a domain of struct dma_ops_domain Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 31/38] lib/genalloc.c: start search from start of chunk Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 32/38] hwrng: core - Dont use a stack buffer in add_early_randomness() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 22/38] scsi: qla2xxx: Fix scsi scan hang triggered if adapter fails during init Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 36/38] mmc: mxs: Initialize the spinlock prior to using it Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 38/38] netfilter: fix namespace handling in nf_log_proc_dostring Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
    Re: [PATCH 4.4 38/38] netfilter: fix namespace handling in  nf_log_proc_dostring Pablo Neira Ayuso <pablo@netfilter.org> - 2016-11-17 12:10 +0100
      Re: [PATCH 4.4 38/38] netfilter: fix namespace handling in  nf_log_proc_dostring Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 13:10 +0100
  [PATCH 4.4 35/38] ASoC: sun4i-codec: return error code instead of NULL when create_card fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 20/38] iio: hid-sensors: Increase the precision of scale to fix wrong reading interpretation. Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 13/38] Revert "staging: nvec: ps2: change serio type to passthrough" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 17/38] drbd: Fix kernel_sendmsg() usage - potential NULL deref Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 37/38] btrfs: qgroup: Prevent qgroup->reserved from going subzero Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 34/38] ACPI / APEI: Fix incorrect return value of ghes_proc() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 12/38] drivers: staging: nvec: remove bogus reset command for PS/2 interface Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 14/38] staging: nvec: remove managed resource from PS2 driver Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 26/38] dmaengine: at_xdmac: fix spurious flag status for mem2mem transfers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 15/38] USB: cdc-acm: fix TIOCMIWAIT Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 09/38] pinctrl: cherryview: Serialize register access in suspend/resume Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 11:50 +0100
  [PATCH 4.4 01/38] ALSA: info: Return error for invalid read/write Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 12:00 +0100
  [PATCH 4.4 03/38] ASoC: cs4270: fix DAPM stream name mismatch Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-11-17 12:00 +0100
  Re: [PATCH 4.4 00/38] 4.4.33-stable review Guenter Roeck <linux@roeck-us.net> - 2016-11-17 23:30 +0100

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