1 files changed, 21 insertions, 9 deletions

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 4ad71ef2cd59..71529e196b84 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -641,7 +641,7 @@ retry:
                 } while (unlikely(entropy_count < pool_size-2 && pnfrac));
         }
 
-        if (entropy_count < 0) {
+        if (unlikely(entropy_count < 0)) {
                 pr_warn("random: negative entropy/overflow: pool %s count %d\n",
                         r->name, entropy_count);
                 WARN_ON(1);
@@ -980,26 +980,37 @@ static void push_to_pool(struct work_struct *work)
 static size_t account(struct entropy_store *r, size_t nbytes, int min,
                       int reserved)
 {
-        int have_bytes;
         int entropy_count, orig;
-        size_t ibytes;
+        size_t ibytes, nfrac;
 
         BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
 
         /* Can we pull enough? */
 retry:
         entropy_count = orig = ACCESS_ONCE(r->entropy_count);
-        have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
         ibytes = nbytes;
         /* If limited, never pull more than available */
-        if (r->limit)
-                ibytes = min_t(size_t, ibytes, have_bytes - reserved);
+        if (r->limit) {
+                int have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
+
+                if ((have_bytes -= reserved) < 0)
+                        have_bytes = 0;
+                ibytes = min_t(size_t, ibytes, have_bytes);
+        }
         if (ibytes < min)
                 ibytes = 0;
-        if (have_bytes >= ibytes + reserved)
-                entropy_count -= ibytes << (ENTROPY_SHIFT + 3);
+
+        if (unlikely(entropy_count < 0)) {
+                pr_warn("random: negative entropy count: pool %s count %d\n",
+                        r->name, entropy_count);
+                WARN_ON(1);
+                entropy_count = 0;
+        }
+        nfrac = ibytes << (ENTROPY_SHIFT + 3);
+        if ((size_t) entropy_count > nfrac)
+                entropy_count -= nfrac;
         else
-                entropy_count = reserved << (ENTROPY_SHIFT + 3);
+                entropy_count = 0;
 
         if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
                 goto retry;
@@ -1375,6 +1386,7 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
                             "with %d bits of entropy available\n",
                             current->comm, nonblocking_pool.entropy_total);
 
+        nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
         ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
 
         trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),