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authorMatt Mackall <mpm@selenic.com>2007-10-07 00:27:53 +0200
committerAdrian Bunk <bunk@kernel.org>2007-10-07 00:27:53 +0200
commit47d9c7762bd6e2d766cba697952f11fba9d5acf6 (patch)
tree7e487af390ac0624d08f141ebf99b5b544490f39
parent46f6fdb65fb9a80fa31ab25c5aad3d150bb7c398 (diff)
random: fix bound check ordering (CVE-2007-3105)
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 <pageexec@freemail.hu>) Signed-off-by: Matt Mackall <mpm@selenic.com> Signed-off-by: Adrian Bunk <bunk@kernel.org>
-rw-r--r--drivers/char/random.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index f162618d0f7f..3b0f11d68408 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -691,9 +691,14 @@ static void xfer_secondary_pool(struct entropy_store *r, size_t nbytes)
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",