[kernel-hardening] [RFC][PATCH 5/7] mm: Mark several cases as SLAB_NO_SANITIZE

Laura Abbott
2015-12-22T03:40:39Z

Sanitization is useful for security but comes at the cost of performance
in clearing on free. Mark select caches as SLAB_NO_SANITIZE so
sanitization will not happen under the default configuration. The
kernel may be booted with the proper command line option to allow these
caches to be sanitized.

All credit for the original work should be given to Brad Spengler and
the PaX Team.

Signed-off-by: Laura Abbott <laura@labbott.name>
---
This is the initial set of excludes that the grsecurity patches had.
More may need to be added/removed as the series is tested.
---
fs/buffer.c | 2 +-
fs/dcache.c | 2 +-
kernel/fork.c | 2 +-
mm/rmap.c | 4 ++--
mm/slab.h | 2 +-
net/core/skbuff.c | 16 ++++++++--------
6 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 4f4cd95..f19e4ab 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3417,7 +3417,7 @@ void __init buffer_init(void)
bh_cachep = kmem_cache_create("buffer_head",
sizeof(struct buffer_head), 0,
(SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
- SLAB_MEM_SPREAD),
+ SLAB_MEM_SPREAD|SLAB_NO_SANITIZE),
NULL);

/*
diff --git a/fs/dcache.c b/fs/dcache.c
index 5c33aeb..470f6be 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3451,7 +3451,7 @@ void __init vfs_caches_init_early(void)
void __init vfs_caches_init(void)
{
names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
- SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
+ SLAB_NO_SANITIZE|SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);

dcache_init();
inode_init();
diff --git a/kernel/fork.c b/kernel/fork.c
index fce002e..35db9c3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1868,7 +1868,7 @@ void __init proc_caches_init(void)
mm_cachep = kmem_cache_create("mm_struct",
sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN,
SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NOTRACK, NULL);
- vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC);
+ vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_NO_SANITIZE);
mmap_init();
nsproxy_cache_init();
}
diff --git a/mm/rmap.c b/mm/rmap.c
index b577fbb..74296d9 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -428,8 +428,8 @@ static void anon_vma_ctor(void *data)
void __init anon_vma_init(void)
{
anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma),
- 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC, anon_vma_ctor);
- anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC);
+ 0, SLAB_DESTROY_BY_RCU|SLAB_PANIC|SLAB_NO_SANITIZE, anon_vma_ctor);
+ anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, SLAB_PANIC|SLAB_NO_SANITIZE);
}

/*
diff --git a/mm/slab.h b/mm/slab.h
index b54b636..6de99da 100644
--- a/mm/slab.h
+++ b/mm/slab.h
@@ -137,7 +137,7 @@ static inline unsigned long kmem_cache_flags(unsigned long object_size,

/* Legal flag mask for kmem_cache_create(), for various configurations */
#define SLAB_CORE_FLAGS (SLAB_HWCACHE_ALIGN | SLAB_CACHE_DMA | SLAB_PANIC | \
- SLAB_DESTROY_BY_RCU | SLAB_DEBUG_OBJECTS )
+ SLAB_DESTROY_BY_RCU | SLAB_DEBUG_OBJECTS | SLAB_NO_SANITIZE)

#if defined(CONFIG_DEBUG_SLAB)
#define SLAB_DEBUG_FLAGS (SLAB_RED_ZONE | SLAB_POISON | SLAB_STORE_USER)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b2df375..1d499ea 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3316,15 +3316,15 @@ done:
void __init skb_init(void)
{
skbuff_head_cache = kmem_cache_create("skbuff_head_cache",
- sizeof(struct sk_buff),
- 0,
- SLAB_HWCACHE_ALIGN|SLAB_PANIC,
- NULL);
+ sizeof(struct sk_buff),
+ 0,
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NO_SANITIZE,
+ NULL);
skbuff_fclone_cache = kmem_cache_create("skbuff_fclone_cache",
- sizeof(struct sk_buff_fclones),
- 0,
- SLAB_HWCACHE_ALIGN|SLAB_PANIC,
- NULL);
+ sizeof(struct sk_buff_fclones),
+ 0,
+ SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_NO_SANITIZE,
+ NULL);
}

/**
--
2.5.0