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-rw-r--r--include/linux/uaccess.h2
-rw-r--r--mm/slab.c22
-rw-r--r--mm/slub.c23
-rw-r--r--mm/usercopy.c21
4 files changed, 58 insertions, 10 deletions
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 38b6442..efe79c1 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -274,6 +274,8 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
#endif
#ifdef CONFIG_HARDENED_USERCOPY
+void usercopy_warn(const char *name, const char *detail, bool to_user,
+ unsigned long offset, unsigned long len);
void __noreturn usercopy_abort(const char *name, const char *detail,
bool to_user, unsigned long offset,
unsigned long len);
diff --git a/mm/slab.c b/mm/slab.c
index 47acfe5..1c02f6e 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4392,7 +4392,9 @@ module_init(slab_proc_init);
#ifdef CONFIG_HARDENED_USERCOPY
/*
- * Rejects objects that are incorrectly sized.
+ * Rejects incorrectly sized objects and objects that are to be copied
+ * to/from userspace but do not fall entirely within the containing slab
+ * cache's usercopy region.
*
* Returns NULL if check passes, otherwise const char * to name of cache
* to indicate an error.
@@ -4412,10 +4414,24 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
/* Find offset within object. */
offset = ptr - index_to_obj(cachep, page, objnr) - obj_offset(cachep);
- /* Allow address range falling entirely within object size. */
- if (offset <= cachep->object_size && n <= cachep->object_size - offset)
+ /* Allow address range falling entirely within usercopy region. */
+ if (offset >= cachep->useroffset &&
+ offset - cachep->useroffset <= cachep->usersize &&
+ n <= cachep->useroffset - offset + cachep->usersize)
return;
+ /*
+ * If the copy is still within the allocated object, produce
+ * a warning instead of rejecting the copy. This is intended
+ * to be a temporary method to find any missing usercopy
+ * whitelists.
+ */
+ if (offset <= cachep->object_size &&
+ n <= cachep->object_size - offset) {
+ usercopy_warn("SLAB object", cachep->name, to_user, offset, n);
+ return;
+ }
+
usercopy_abort("SLAB object", cachep->name, to_user, offset, n);
}
#endif /* CONFIG_HARDENED_USERCOPY */
diff --git a/mm/slub.c b/mm/slub.c
index f40a571..6d9b1e7 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3813,7 +3813,9 @@ EXPORT_SYMBOL(__kmalloc_node);
#ifdef CONFIG_HARDENED_USERCOPY
/*
- * Rejects objects that are incorrectly sized.
+ * Rejects incorrectly sized objects and objects that are to be copied
+ * to/from userspace but do not fall entirely within the containing slab
+ * cache's usercopy region.
*
* Returns NULL if check passes, otherwise const char * to name of cache
* to indicate an error.
@@ -3827,7 +3829,6 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
/* Find object and usable object size. */
s = page->slab_cache;
- object_size = slab_ksize(s);
/* Reject impossible pointers. */
if (ptr < page_address(page))
@@ -3845,10 +3846,24 @@ void __check_heap_object(const void *ptr, unsigned long n, struct page *page,
offset -= s->red_left_pad;
}
- /* Allow address range falling entirely within object size. */
- if (offset <= object_size && n <= object_size - offset)
+ /* Allow address range falling entirely within usercopy region. */
+ if (offset >= s->useroffset &&
+ offset - s->useroffset <= s->usersize &&
+ n <= s->useroffset - offset + s->usersize)
return;
+ /*
+ * If the copy is still within the allocated object, produce
+ * a warning instead of rejecting the copy. This is intended
+ * to be a temporary method to find any missing usercopy
+ * whitelists.
+ */
+ object_size = slab_ksize(s);
+ if (offset <= object_size && n <= object_size - offset) {
+ usercopy_warn("SLUB object", s->name, to_user, offset, n);
+ return;
+ }
+
usercopy_abort("SLUB object", s->name, to_user, offset, n);
}
#endif /* CONFIG_HARDENED_USERCOPY */
diff --git a/mm/usercopy.c b/mm/usercopy.c
index a562dd0..e9e9325 100644
--- a/mm/usercopy.c
+++ b/mm/usercopy.c
@@ -59,13 +59,28 @@ static noinline int check_stack_object(const void *obj, unsigned long len)
}
/*
- * If this function is reached, then CONFIG_HARDENED_USERCOPY has found an
- * unexpected state during a copy_from_user() or copy_to_user() call.
+ * If these functions are reached, then CONFIG_HARDENED_USERCOPY has found
+ * an unexpected state during a copy_from_user() or copy_to_user() call.
* There are several checks being performed on the buffer by the
* __check_object_size() function. Normal stack buffer usage should never
* trip the checks, and kernel text addressing will always trip the check.
- * For cache objects, copies must be within the object size.
+ * For cache objects, it is checking that only the whitelisted range of
+ * bytes for a given cache is being accessed (via the cache's usersize and
+ * useroffset fields). To adjust a cache whitelist, use the usercopy-aware
+ * kmem_cache_create_usercopy() function to create the cache (and
+ * carefully audit the whitelist range).
*/
+void usercopy_warn(const char *name, const char *detail, bool to_user,
+ unsigned long offset, unsigned long len)
+{
+ WARN_ONCE(1, "Bad or missing usercopy whitelist? Kernel memory %s attempt detected %s %s%s%s%s (offset %lu, size %lu)!\n",
+ to_user ? "exposure" : "overwrite",
+ to_user ? "from" : "to",
+ name ? : "unknown?!",
+ detail ? " '" : "", detail ? : "", detail ? "'" : "",
+ offset, len);
+}
+
void __noreturn usercopy_abort(const char *name, const char *detail,
bool to_user, unsigned long offset,
unsigned long len)
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