diff options
authorJarod Wilson <jarod@redhat.com>2013-05-24 15:55:31 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-24 16:22:52 -0700
commit1e7e2e05c179a68aaf8830fe91547a87f4589e53 (patch)
parent348f9f05e0266822fa048f7fb3b039692a0cafbc (diff)
drivers/char/random.c: fix priming of last_data
Commit ec8f02da9ea5 ("random: prime last_data value per fips requirements") added priming of last_data per fips requirements. Unfortuantely, it did so in a way that can lead to multiple threads all incrementing nbytes, but only one actually doing anything with the extra data, which leads to some fun random corruption and panics. The fix is to simply do everything needed to prime last_data in a single shot, so there's no window for multiple cpus to increment nbytes -- in fact, we won't even increment or decrement nbytes anymore, we'll just extract the needed EXTRACT_SIZE one time per pool and then carry on with the normal routine. All these changes have been tested across multiple hosts and architectures where panics were previously encoutered. The code changes are are strictly limited to areas only touched when when booted in fips mode. This change should also go into 3.8-stable, to make the myriads of fips users on 3.8.x happy. Signed-off-by: Jarod Wilson <jarod@redhat.com> Tested-by: Jan Stancek <jstancek@redhat.com> Tested-by: Jan Stodola <jstodola@redhat.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: Neil Horman <nhorman@tuxdriver.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Matt Mackall <mpm@selenic.com> Cc: "Theodore Ts'o" <tytso@mit.edu> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 15 insertions, 15 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index cd9a6211dcad..73e52b7796f9 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -957,10 +957,23 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
ssize_t ret = 0, i;
__u8 tmp[EXTRACT_SIZE];
+ unsigned long flags;
/* if last_data isn't primed, we need EXTRACT_SIZE extra bytes */
- if (fips_enabled && !r->last_data_init)
- nbytes += EXTRACT_SIZE;
+ if (fips_enabled) {
+ spin_lock_irqsave(&r->lock, flags);
+ if (!r->last_data_init) {
+ r->last_data_init = true;
+ spin_unlock_irqrestore(&r->lock, flags);
+ trace_extract_entropy(r->name, EXTRACT_SIZE,
+ r->entropy_count, _RET_IP_);
+ xfer_secondary_pool(r, EXTRACT_SIZE);
+ extract_buf(r, tmp);
+ spin_lock_irqsave(&r->lock, flags);
+ memcpy(r->last_data, tmp, EXTRACT_SIZE);
+ }
+ spin_unlock_irqrestore(&r->lock, flags);
+ }
trace_extract_entropy(r->name, nbytes, r->entropy_count, _RET_IP_);
xfer_secondary_pool(r, nbytes);
@@ -970,19 +983,6 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
extract_buf(r, tmp);
if (fips_enabled) {
- unsigned long flags;
- /* prime last_data value if need be, per fips 140-2 */
- if (!r->last_data_init) {
- spin_lock_irqsave(&r->lock, flags);
- memcpy(r->last_data, tmp, EXTRACT_SIZE);
- r->last_data_init = true;
- nbytes -= EXTRACT_SIZE;
- spin_unlock_irqrestore(&r->lock, flags);
- extract_buf(r, tmp);
- }
spin_lock_irqsave(&r->lock, flags);
if (!memcmp(tmp, r->last_data, EXTRACT_SIZE))
panic("Hardware RNG duplicated output!\n");