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Groups > linux.kernel > #1670053

[PATCH 02/23] usercopy: Enforce slab cache usercopy region boundaries

From Kees Cook <keescook@chromium.org>
Newsgroups linux.kernel
Subject [PATCH 02/23] usercopy: Enforce slab cache usercopy region boundaries
Date 2017-06-20 01:50 +0200
Message-ID <tUeAG-U8-29@gated-at.bofh.it> (permalink)
References <tUeqZ-QH-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

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From: David Windsor <dave@nullcore.net>

This patch adds the enforcement component of usercopy cache whitelisting,
and is modified from Brad Spengler/PaX Team's PAX_USERCOPY whitelisting
code in the last public patch of grsecurity/PaX based on my understanding
of the code. Changes or omissions from the original code are mine and
don't reflect the original grsecurity/PaX code.

The SLAB and SLUB allocators are modified to deny all copy operations
in which the kernel heap memory being modified falls outside of the cache's
defined usercopy region.

Signed-off-by: David Windsor <dave@nullcore.net>
[kees: adjust commit log and comments]
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 mm/slab.c | 16 +++++++++++-----
 mm/slub.c | 18 +++++++++++-------
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index cf77f1691588..5c78830aeea0 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4416,7 +4416,9 @@ 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.
@@ -4436,11 +4438,15 @@ const char *__check_heap_object(const void *ptr, unsigned long n,
 	/* 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)
-		return NULL;
+	/* Make sure object falls entirely within cache's usercopy region. */
+	if (offset < cachep->useroffset)
+		return cachep->name;
+	if (offset - cachep->useroffset > cachep->usersize)
+		return cachep->name;
+	if (n > cachep->useroffset - offset + cachep->usersize)
+		return cachep->name;
 
-	return cachep->name;
+	return NULL;
 }
 #endif /* CONFIG_HARDENED_USERCOPY */
 
diff --git a/mm/slub.c b/mm/slub.c
index b8cbbc31b005..e12a2bfbca1e 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -3796,7 +3796,9 @@ 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.
@@ -3806,11 +3808,9 @@ const char *__check_heap_object(const void *ptr, unsigned long n,
 {
 	struct kmem_cache *s;
 	unsigned long offset;
-	size_t object_size;
 
 	/* Find object and usable object size. */
 	s = page->slab_cache;
-	object_size = slab_ksize(s);
 
 	/* Reject impossible pointers. */
 	if (ptr < page_address(page))
@@ -3826,11 +3826,15 @@ const char *__check_heap_object(const void *ptr, unsigned long n,
 		offset -= s->red_left_pad;
 	}
 
-	/* Allow address range falling entirely within object size. */
-	if (offset <= object_size && n <= object_size - offset)
-		return NULL;
+	/* Make sure object falls entirely within cache's usercopy region. */
+	if (offset < s->useroffset)
+		return s->name;
+	if (offset - s->useroffset > s->usersize)
+		return s->name;
+	if (n > s->useroffset - offset + s->usersize)
+		return s->name;
 
-	return s->name;
+	return NULL;
 }
 #endif /* CONFIG_HARDENED_USERCOPY */
 
-- 
2.7.4

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Thread

[PATCH 00/23] Hardened usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 13/23] ufs: define usercopy region in ufs_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 22/23] usercopy: split user-controlled slabs to separate caches Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
    Re: [kernel-hardening] [PATCH 22/23] usercopy: split user-controlled  slabs to separate caches Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:30 +0200
    Re: [kernel-hardening] [PATCH 22/23] usercopy: split user-controlled  slabs to separate caches Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:50 +0200
      Re: [kernel-hardening] [PATCH 22/23] usercopy: split user-controlled  slabs to separate caches Kees Cook <keescook@chromium.org> - 2017-06-21 00:30 +0200
    Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate  caches Laura Abbott <labbott@redhat.com> - 2017-06-20 22:30 +0200
      Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate caches Kees Cook <keescook@chromium.org> - 2017-06-21 00:30 +0200
        Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate  caches Michal Hocko <mhocko@kernel.org> - 2017-06-27 09:40 +0200
          Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate caches Kees Cook <keescook@chromium.org> - 2017-06-28 00:10 +0200
            Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate  caches Michal Hocko <mhocko@kernel.org> - 2017-06-28 11:00 +0200
  [PATCH 08/23] ext2: define usercopy region in ext2_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 15/23] net: define usercopy region in struct proto slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 14/23] fork: define usercopy region in thread_stack, task_struct, mm_struct slab caches Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 11/23] jfs: define usercopy region in jfs_ip slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 20/23] usercopy: convert kmalloc caches to usercopy caches Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 05/23] befs: define usercopy region in befs_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 23/23] mm: Allow slab_nomerge to be set at build time Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
    Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be  set at build time Daniel Micay <danielmicay@gmail.com> - 2017-06-20 06:10 +0200
      Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be set  at build time Kees Cook <keescook@chromium.org> - 2017-06-21 01:00 +0200
    Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be  set at build time Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:30 +0200
      Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be set  at build time Kees Cook <keescook@chromium.org> - 2017-06-21 01:20 +0200
  [PATCH 19/23] xfs: define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 01/23] usercopy: Prepare for usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 03/23] vfs: define usercopy region in names_cache slab caches Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 17/23] dcache: define usercopy region in dentry_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
    Re: [kernel-hardening] [PATCH 17/23] dcache: define usercopy region  in dentry_cache slab cache Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:10 +0200
      Re: [kernel-hardening] [PATCH 17/23] dcache: define usercopy region  in dentry_cache slab cache Eric Biggers <ebiggers3@gmail.com> - 2017-06-28 20:00 +0200
      Re: [kernel-hardening] [PATCH 17/23] dcache: define usercopy region  in dentry_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-28 20:00 +0200
  [PATCH 04/23] vfs: copy struct mount.mnt_id to userspace using put_user() Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 06/23] cifs: define usercopy region in cifs_request slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 21/23] usercopy: Restrict non-usercopy caches to size 0 Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
    Re: [kernel-hardening] [PATCH 21/23] usercopy: Restrict non-usercopy  caches to size 0 Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:10 +0200
      Re: [kernel-hardening] [PATCH 21/23] usercopy: Restrict non-usercopy  caches to size 0 Kees Cook <keescook@chromium.org> - 2017-06-28 20:00 +0200
  [PATCH 18/23] scsi: define usercopy region in scsi_sense_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 02/23] usercopy: Enforce slab cache usercopy region boundaries Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  Re: [kernel-hardening] [PATCH 00/23] Hardened usercopy whitelisting Rik van Riel <riel@redhat.com> - 2017-06-20 21:50 +0200

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