From: Nicolas Pennequin <nicolas.pennequin@free.fr>
Date: Sat, 4 Aug 2007 18:26:58 +0000 (+0200)
Subject: bufgetdata: Check that the caller isn't too greedy.
X-Git-Tag: working_mob~1
X-Git-Url: https://repo.or.cz/w/Rockbox-MoB.git/commitdiff_plain/d1be61dc61c4746059b3ef48bce4d942c3382514

bufgetdata: Check that the caller isn't too greedy.

When the buffer wraps and we need to use the guard buffer to provide a complete chunk,
there is a limit to the amount of data we can provide. It's unsafe to assume we can
provide the requested amount of data.
---

diff --git a/testplugin.c b/testplugin.c
index 3020b2d..64457a5 100644
--- a/testplugin.c
+++ b/testplugin.c
@@ -637,9 +637,9 @@ ssize_t bufgetdata(int handle_id, size_t size, unsigned char **data)
         h->available - RINGBUF_SUB(h->ridx, h->data) >= size)
     {
         /* use the guard buffer to provide what was requested. */
-        size_t copy_n = h->ridx + size - buffer_len;
+        size_t copy_n = MIN(h->ridx + size - buffer_len, GUARD_SIZE);
         rb->memcpy(guard_buffer, (unsigned char *)buffer, copy_n);
-        ret = size;
+        ret = buffer_len - h->ridx + copy_n;
         DEBUGF("used the guard buffer to complete\n");
     }
     else