diff options
| author | Matt Mackall <mpm@selenic.com> | 2007-07-19 11:30:14 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-07-19 14:21:04 -0700 |
| commit | 5a021e9ffd56c22700133ebc37d607f95be8f7bd (patch) | |
| tree | 0d289c7feec4e7b3b19c7c312e8cb31532c5b9c9 | |
| parent | f745bb1c73e2395e6b9961d4d915a8f8e2cd32cd (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>)
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>
| -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 7f5271272f9..397c714cf2b 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", |