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author | David Windsor <dave@nullcore.net> | 2017-08-16 01:45:00 +0200 |
---|---|---|
committer | Kees Cook <keescook@chromium.org> | 2018-01-15 21:08:02 +0100 |
commit | 07dcd7fe89938934ddad65f738bc5aac89b8e54d (patch) | |
tree | 717298a13dce63c41306a91baf77201acc1c1b4f /kernel/fork.c | |
parent | net: Restrict unwhitelisted proto caches to size 0 (diff) | |
download | linux-07dcd7fe89938934ddad65f738bc5aac89b8e54d.tar.xz linux-07dcd7fe89938934ddad65f738bc5aac89b8e54d.zip |
fork: Define usercopy region in mm_struct slab caches
In support of usercopy hardening, this patch defines a region in the
mm_struct slab caches in which userspace copy operations are allowed.
Only the auxv field is copied to userspace.
cache object allocation:
kernel/fork.c:
#define allocate_mm() (kmem_cache_alloc(mm_cachep, GFP_KERNEL))
dup_mm():
...
mm = allocate_mm();
copy_mm(...):
...
dup_mm();
copy_process(...):
...
copy_mm(...)
_do_fork(...):
...
copy_process(...)
example usage trace:
fs/binfmt_elf.c:
create_elf_tables(...):
...
elf_info = (elf_addr_t *)current->mm->saved_auxv;
...
copy_to_user(..., elf_info, ei_index * sizeof(elf_addr_t))
load_elf_binary(...):
...
create_elf_tables(...);
This region is known as the slab cache's usercopy region. Slab caches
can now check that each dynamically sized copy operation involving
cache-managed memory falls entirely within the slab's usercopy region.
This patch 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.
Signed-off-by: David Windsor <dave@nullcore.net>
[kees: adjust commit log, split patch, provide usage trace]
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Acked-by: Rik van Riel <riel@redhat.com>
Diffstat (limited to 'kernel/fork.c')
-rw-r--r-- | kernel/fork.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 432eadf6b58c..82f2a0441d3b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2225,9 +2225,11 @@ void __init proc_caches_init(void) * maximum number of CPU's we can ever have. The cpumask_allocation * is at the end of the structure, exactly for that reason. */ - mm_cachep = kmem_cache_create("mm_struct", + mm_cachep = kmem_cache_create_usercopy("mm_struct", sizeof(struct mm_struct), ARCH_MIN_MMSTRUCT_ALIGN, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, + offsetof(struct mm_struct, saved_auxv), + sizeof_field(struct mm_struct, saved_auxv), NULL); vm_area_cachep = KMEM_CACHE(vm_area_struct, SLAB_PANIC|SLAB_ACCOUNT); mmap_init(); |