[PATCH] fix broken size test in bitmap_find_free_region()

Guennadi Liakhovetski
2009-02-06T12:22:38Z

This loop and test in bitmap_find_free_region()

for (pos = 0; pos < bits; pos += (1 << order))
if (__reg_op(bitmap, pos, order, REG_OP_ISFREE))
break;
if (pos == bits)
return -ENOMEM;

can only return an error (-ENOMEM) if bits is a multiple of (1 << order),
which is, for instance, true, if bits is (also) a power of 2. This
is not necessarily the case with dma_alloc_from_coherent(). A failure to
recognise too large a request leads in dma_alloc_from_coherent() to
accessing beyond available memory, and to writing beyond the bitmap.

Signed-off-by: Guennadi Liakhovetski <lg@denx.de>
---

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 1338469..d49c37f 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -953,7 +953,7 @@ int bitmap_find_free_region(unsigned long *bitmap, int bits, int order)
for (pos = 0; pos < bits; pos += (1 << order))
if (__reg_op(bitmap, pos, order, REG_OP_ISFREE))
break;
- if (pos == bits)
+ if (pos + (1 << order) > bits)
return -ENOMEM;
__reg_op(bitmap, pos, order, REG_OP_ALLOC);
return pos;