random: fix bound check ordering (CVE-2007-3105) (5a021e9f) · Commits · 戴 / test

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>) Cc: Theodore Tso <tytso@mit.edu> Cc: Willy Tarreau <w@1wt.eu> Signed-off-by:

Matt Mackall <mpm@selenic.com> Signed-off-by:

Chris Wright <chrisw@sous-sol.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/random.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -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",

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