diff options
| author | Matt Mackall <mpm@selenic.com> | 2007-10-07 00:27:53 +0200 |
|---|---|---|
| committer | Adrian Bunk <bunk@kernel.org> | 2007-10-07 00:27:53 +0200 |
| commit | 47d9c7762bd6e2d766cba697952f11fba9d5acf6 (patch) | |
| tree | 7e487af390ac0624d08f141ebf99b5b544490f39 | |
| parent | 46f6fdb65fb9a80fa31ab25c5aad3d150bb7c398 (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.c | 9 |
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", |