[PATCH] fix broken lib/genalloc.c

[Chris Humbert <mahadri-kernel@drigon.com>]

genalloc improperly stores the size of freed chunks, allocates
overlapping memory regions, and oopses after its in-band data is
overwritten.  Jes Sorensen's original patch to LKML used:

> +	s = (1 << ALLOC_MIN_SHIFT);
> +	while (size > s) {
> +		s <<= 1;
> +		i++;
> +	}

After Andrew Morton suggested roundup_pow_of_two(), Jes changed
it to:

> +	size = max(size, 1 << ALLOC_MIN_SHIFT);
> +	s = roundup_pow_of_two(size);

but this does not set 'i'.  I have verified that genalloc with
the attached patch works correctly.

Chris Humbert



[PATCH] fix broken lib/genalloc.c

genalloc improperly stores the sizes of freed chunks, allocates
overlapping memory regions, and oopses after its in-band data is
overwritten.

Signed-off-by: Chris Humbert <mahadri-kernel@drigon.com>

diff --git a/lib/genalloc.c b/lib/genalloc.c
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -95,12 +95,10 @@ unsigned long gen_pool_alloc(struct gen_
 	if (size > max_chunk_size)
 		return 0;
 
-	i = 0;
-
 	size = max(size, 1 << ALLOC_MIN_SHIFT);
-	s = roundup_pow_of_two(size);
-
-	j = i;
+	i = fls(size - 1);
+	s = 1 << i;
+	j = i -= ALLOC_MIN_SHIFT;
 
 	spin_lock_irqsave(&poolp->lock, flags);
 	while (!h[j].next) {
@@ -153,10 +151,10 @@ void gen_pool_free(struct gen_pool *pool
 	if (size > max_chunk_size)
 		return;
 
-	i = 0;
-
 	size = max(size, 1 << ALLOC_MIN_SHIFT);
-	s = roundup_pow_of_two(size);
+	i = fls(size - 1);
+	s = 1 << i;
+	i -= ALLOC_MIN_SHIFT;
 
 	a = ptr;