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authorMatt Mackall <mpm@selenic.com>2007-07-19 11:30:14 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-07-19 14:21:04 -0700
commit5a021e9ffd56c22700133ebc37d607f95be8f7bd (patch)
tree0d289c7feec4e7b3b19c7c312e8cb31532c5b9c9
parentf745bb1c73e2395e6b9961d4d915a8f8e2cd32cd (diff)
downloadlinux-linaro-5a021e9ffd56c22700133ebc37d607f95be8f7bd.tar.gz
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.c9
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",