[PATCH v2 15/19] malloc: implement free_sensitive()

[Sascha Hauer <s.hauer@pengutronix.de>]

barebox sometimes stores sensitive data in memory. Add a
(k)free_sensitive() function which zeroes out the memory before freeing it.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 common/dlmalloc.c    | 15 +++++++++++++++
 common/tlsf_malloc.c | 11 +++++++++++
 include/dma.h        |  5 +++++
 include/linux/slab.h |  5 +++++
 include/malloc.h     |  1 +
 5 files changed, 37 insertions(+)

diff --git a/common/dlmalloc.c b/common/dlmalloc.c
index c41487d54b..0e23399b2b 100644
--- a/common/dlmalloc.c
+++ b/common/dlmalloc.c
@@ -1431,6 +1431,21 @@ void free(void *mem)
 		frontlink(p, sz, idx, bck, fwd);
 }
 
+void free_sensitive(void *mem)
+{
+	mchunkptr p;
+	size_t size;
+
+	if (!mem)
+		return;
+
+	p = mem2chunk(mem);
+	size = chunksize(p);
+	if (size)
+		memset(mem, size, 0x0);
+
+	free(mem);
+}
 /*
   Realloc algorithm:
 
diff --git a/common/tlsf_malloc.c b/common/tlsf_malloc.c
index 981f09de41..5bcbbcd2f8 100644
--- a/common/tlsf_malloc.c
+++ b/common/tlsf_malloc.c
@@ -38,6 +38,17 @@ void free(void *mem)
 }
 EXPORT_SYMBOL(free);
 
+void free_sensitive(void *mem)
+{
+	size_t size;
+
+	size = tlsf_block_size(mem);
+	if (size)
+		memset(mem, size, 0x0);
+
+	tlsf_free(tlsf_mem_pool, mem);
+}
+
 void *realloc(void *oldmem, size_t bytes)
 {
 	void *mem = tlsf_realloc(tlsf_mem_pool, oldmem, bytes);
diff --git a/include/dma.h b/include/dma.h
index 4fcd114bb6..c2b1bee358 100644
--- a/include/dma.h
+++ b/include/dma.h
@@ -41,6 +41,11 @@ static inline void dma_free(void *mem)
 	free(mem);
 }
 
+static inline void dma_free_sensitive(void *mem)
+{
+	free_sensitive(mem);
+}
+
 #define DMA_BIT_MASK(n)	(((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
 
 #define DMA_MASK_NONE	0x0ULL
diff --git a/include/linux/slab.h b/include/linux/slab.h
index eba3593d75..8c82e19866 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -67,6 +67,11 @@ static inline void kfree(const void *mem)
 	dma_free((void *)mem);
 }
 
+static inline void kfree_sensitive(const void *objp)
+{
+	dma_free_sensitive((void *)objp);
+}
+
 static inline void *kmem_cache_alloc(struct kmem_cache *cache, gfp_t flags)
 {
 	void *mem = kmalloc(cache->size, flags);
diff --git a/include/malloc.h b/include/malloc.h
index d63853b91e..c25bbf6949 100644
--- a/include/malloc.h
+++ b/include/malloc.h
@@ -7,6 +7,7 @@
 
 void *malloc(size_t) __alloc_size(1);
 void free(void *);
+void free_sensitive(void *);
 void *realloc(void *, size_t) __realloc_size(2);
 void *memalign(size_t, size_t) __alloc_size(2);
 void *calloc(size_t, size_t) __alloc_size(1, 2);
-- 
2.39.2