From: Matt Mackall Date: Thu, 19 Jul 2007 18:30:14 +0000 (-0700) Subject: random: fix bound check ordering (CVE-2007-3105) X-Git-Tag: v2.6.23-rc1~259 X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=5a021e9ffd56c22700133ebc37d607f95be8f7bd 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 ) Cc: Theodore Tso Cc: Willy Tarreau Signed-off-by: Matt Mackall Signed-off-by: Chris Wright Signed-off-by: Linus Torvalds --- diff --git a/drivers/char/random.c b/drivers/char/random.c index 7f52712..397c714 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -693,9 +693,14 @@ 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",