-stable review patch. If anyone has any objections, please let us know.
------------------
From: Matt Mackall <[email protected]>
If root raised the default wakeup threshold over the size of the
output pool, the pool transfer function could overflow the stack with
RNG bytes, causing a DoS or potential privilege escalation.
(Bug reported by the PaX Team <[email protected]>)
Cc: Theodore Tso <[email protected]>
Cc: Willy Tarreau <[email protected]>
Signed-off-by: Matt Mackall <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/char/random.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -693,9 +693,14 @@ static void xfer_secondary_pool(struct e
if (r->pull && r->entropy_count < nbytes * 8 &&
r->entropy_count < r->poolinfo->POOLBITS) {
- int bytes = max_t(int, random_read_wakeup_thresh / 8,
- min_t(int, nbytes, sizeof(tmp)));
+ /* If we're limited, always leave two wakeup worth's BITS */
int rsvd = r->limit ? 0 : random_read_wakeup_thresh/4;
+ int bytes = nbytes;
+
+ /* pull at least as many as BYTES as wakeup BITS */
+ bytes = max_t(int, bytes, random_read_wakeup_thresh / 8);
+ /* but never more than the buffer size */
+ bytes = min_t(int, bytes, sizeof(tmp));
DEBUG_ENT("going to reseed %s with %d bits "
"(%d of %d requested)\n",
--
-
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